A series of new pyridine carboxamide complexes and self-assemblies with Tb(III), Eu(III), Zn(II), Cu(II) ions and their luminescent and magnetic properties

Abstract In this study, we present eight new complexes and self-assemblies of Tb(III), Eu(III), Zn(II) and Cu(II) ions with novel pyridine carboxamides, L1 [methyl 4-methyl-3-(pyridine-4-carbonylamino)benzoate] and L2 [methyl 2-methyl-3-(pyridine-4-carbonylamino)benzoate], as heterocyclic ligands. Two luminescent and spatially organized coordination compounds were obtained with the use of the solvothermal synthesis method, (1) [Tb3(L1)4(BTC)3(H2O)3] (where BTC is benzene-1,3,5-tricarboxylic acid) and (5) [Eu(L2a)3(H2O)3](H2O)4. As a result of one pot reaction synthesis under reflux the d-electron metal ions and self-organization of ligands gave complexes (2) [Zn(L1)2Cl2], (3) [Cu(L1)2(SCN)2(H2O)], (4) [Cu(L1)2Cl2], hybrid salt (6) [(CuCl4)2-(L2b)22+](H2O), (7) [Cu(L2)2Cl2] and 1D-chain coordination polymer (8) [Cu(L2)2(SCN)2]. Identification of the obtained compounds was performed on the basis of the excitation, emission, 1H NMR, FT-IR spectra, luminescence lifetimes, SEM images, PXRD, single-crystal X-ray diffraction, MS, TGA and elemental analysis. Selected compounds were also analyzed in terms of their potential magnetic properties. Graphical Abstract

In continuation of our previous works and to contribute to the knowledge of the chemistry of pyridinecarboxylic acid amides, in this article the preparation as well as spectroscopic and structural characterization of complexes of new pyridine carboxylic acid amide ligands ([methyl 2-methyl-3-(pyridine-4-carbonylamino)benzoate and methyl 4-methyl-3-(pyridine-4-carbonylamino)benzoate]) with d-and f-electron metal ions are described.

Experimental
Chemicals and solvents for the synthesis, as commercially received in analytical grade, were used without purification. The carboxamide heterocyclic ligands L1 and L2, L2a, L2b (Scheme 1) have been obtained and characterized previously [12a]. All metal ion salts used for the presented syntheses, zinc(II) tetrafluoroborate, copper(II) tetrafluoroborate, copper(II) chloride, BTC and ammonium thiocyanate, were purchased from Sigma-Aldrich/MERCK. Europium acetate and terbium chloride were prepared from Eu 2 O 3 and Tb 4 O 7 (Stanford Materials Corporation). The methanol solvent, sodium hydroxide, hydrochloric and acetic acid were acquired from Avantor Performance Materials Poland S.A.
2.1. Synthesis of [Tb 3 (L1) 4 (BTC) 3 (H 2 O) 3 ] (1) triaqua tris(benzene-1,3,5tricarboxylate) tetrakis[methyl 4-methyl-3-(pyridine-4carbonylamino)benzoate]triterbium(III) In 10 mL of distilled water was dissolved TbCl 3 Á6H 2 O (0.1867 g, 0.0005 mol). Then, a portion of 0.1534 g (0.0005 mol) of L1 dissolved in methanol/water (4 mL/2 mL) was added dropwise to the mixture. After 30 min of stirring, 0.1051 g (0.0005 mol) of BTC and 0.0600 g (0.0015 mol) of NaOH were dissolved together in H 2 O and then added dropwise to the reaction mixture and stirred for 1 h at room temperature. The pH of the mixture was adjusted to $7.00 with the use of NaOH aq. solution. The white suspension ($30 mL) was then poured into the Teflon-lined vessel and transported to a stainless steel solvothermal reactor. The reaction took 24 h, at 120 C. After 24 h, the reactor was stopped and cooled freely to room temperature. The precipitated white needle crystals of final product were filtered off and washed with distilled water (yield: 0.2177 g, 78% based on L1).
To a solution of Cu(BF 4 ) 2 ÁxH 2 O (0.0593 g, $0.2500 mmol) in MeOH (5 mL), a solution of L1 (0.0767 g, 0.2500 mmol) in equal volume of MeOH was added dropwise and stirred for 30 min. Then, 0.0190 g (0.2500 mmol) of NH 4 SCN solution in MeOH (5 mL) was added dropwise to the other reactants in the reaction flask. The final reaction mixture was stirred for 3 h at 60 C under reflux. The bright green needles precipitated after a few days of exposure to air. The precipitated product was filtered off and washed with a small amount of distilled water and MeOH (yield: 0.0664 g, 72% based on L1).

Synthesis of [Eu(L2a) 3 (H 2 O) 3 ] (H 2 O) 4 (5) triaqua tris[2-methyl-3-(pyridine-4carbonylamino)benzoate]europium(III) tetrahydrate
To a water (10 mL) solution of Eu(CH 3 COO) 3 Á4H 2 O 0.2006 g (0.0005 mol), a solution of L2 0.1624 g (0.0005 mol) in a water/methanol (6 mL/2 mL) mixture was added dropwise. The pH was adjusted to 7.00 with the use of NaOH aq. solution. Then the obtained white suspension was transported to a Teflon-lined vessel and heated in a stainless steel solvothermal reactor for 3 days at 160 C. After 3 days, the reactor was stopped and cooled freely to room temperature. The final mixture obtained turned a bright orange color and white flakes crystalized after a few days of evaporation. The precipitated flakes of final product were filtered off and washed with distilled water (yield: 0.0696 g, 38% based on L2).

Materials and methods
The percentage contributions of carbon, nitrogen and hydrogen were obtained with the use of an Elementar model Vario EL III CHN analyzer. Mass spectrometry measurements (ESI-MS) were recorded with the use of MeOH solvent on a Waters HPLC/MS Chromatograph. The 1 H NMR spectra of 1 and 5 were recorded in d 6 -DMSO solutions on a Bruker Ascend TM 600 MHz and Varian VNMR-S 400 MHz. All FT-IR spectra were recorded on a Jasco FT/IR-4200 spectrophotometer in the spectral range 4000-400 cm À1 . The measurements were carried out as KBr pellets. The solvothermal syntheses were carried out in a DAB-2 Pressure Digestion System (Berghof Products þ Instruments GmbH) reactor in Teflon-lined vessels. The SEM images were obtained with a JEOL 5200 LV SEM (scanning electron microscope) from JEOL Ltd. (Tokyo, Japan). The SEM-EDS quantitative analysis and mapping of the chemical composition of the samples were carried out on a High Resolution Environmental Scanning Electron Microscope (Quanta 250 FEG, FEI). The TG-DTA measurements were carried out using a thermogravimetric analyzer (TGA 4000, Perkin Elmer).
Excitation and emission spectra in the solid state were measured using an F-7000, Hitachi Fluorescence Spectrophotometer at room temperature. Solid samples for emission measurements were used in the forms obtained in the synthesis reactions. In order to obtain reliable and accurate data, the solid state samples were measured within the same sample holder to ensure the consistent amount of luminescent materials in all samples. Excitation and emission spectra were corrected for the instrumental response. All measurements were carried out under the same experimental conditions. Luminescence lifetimes and measurements of decay curves of samples in solid state were performed with the use of a QuantaMaster TM 40 (Photon Technology International) spectrophotometer equipped with an Opolette 355LD UVDM (Opotek Incorporation) tunable laser (excitation source), with a repetition rate of 20 Hz, and Hamamatsu R928 or R5108 photo-multipliers used as detectors at room temperature. Chromaticity diagrams were generated with the use of the Origin template worksheet from the OriginLab website [13].
Powder XRD measurements were recorded on a Bruker AXS D8 Advance diffractometer in the range 6-60st 2th/step 0.05st 2th/1s for step. Single-crystal diffraction data were collected at room temperature (2, 7) and at 100(1) K (6, 8) by the x-scan technique on a Rigaku Xcalibur four-circle diffractometer with Eos CCD detector and graphite-monochromated MoKa radiation (k ¼ 0.71069 Å). The data were corrected for Lorentz-polarization as well as for absorption effects [14a]. Precise unit-cell parameters were determined by the least-squares fit of 3141 (2), 4470 (6), 3366 (7) and 3502 (8) reflections of the highest intensity, chosen from the whole experiment. The structures were solved with SHELXT [14b] and refined with the full-matrix least-squares procedure on F 2 by SHELXL-2013 [14c]. All non-hydrogen atoms were refined anisotropically. NH hydrogen atoms in 2 were found in difference Fourier maps and freely refined; all other hydrogen atoms were placed in idealized positions and refined as a "riding model" with isotropic displacement parameters set at 1.2 (1.5 for methyl groups) times U eq of the appropriate carrier atom. Table 1 lists the relevant crystal data and refinement details.
The magnetic susceptibility of 1 was studied in the range 2-299 K with the use of a Quantum Design SQUID-VSM magnetometer. A superconducting magnet was generally operated at a field strength ranging from 0 to 7 T. Measurements were made at a magnetic field 0.1 T. The SQUID magnetometer was calibrated with the palladium rod sample. Corrections for diamagnetism of the constituent atoms were calculated using Pascal's constants [15a,b].
Effective magnetic moment values were calculated from the equation: where l eff is the effective magnetic moment, v M corr is the magnetic susceptibility per mole and T is absolute temperature. The magnetic dc susceptibility of 3, 4, 7 and 8 was measured using the Quantum Design VSM option of the Physical Property Measurement System (PPMS). The samples were placed in standard QD VSM holders. Temperature dependence of the magnetic susceptibility v(T) was determined both in the zero field cooled (ZFC) and field cooled (FC) mode in the temperature range 1.9-300 K and at a magnetic field m 0 H ¼ 0.5 T. No difference between the ZFC and FC curves was detected, therefore only the FC results are presented. The same magnetic field and temperature as applied for measurements of the holder with the samples studied were used for measurements of an empty holder to eliminate the signals not coming from the samples. For the magnetic measurements, the empty holder including any wrapping has been first measured in identical magnetic fields and temperatures as for the measurements including the sample and then subtracted from the total signal. The correction for the sample diamagnetic contribution made according to Ref. [16]. Magnetization curves M(H) were measured at temperature T ¼ 2 K for magnetic fields ranging from 0 to 9 T. Full hysteresis loops were determined; however, only the first quarter is displayed in this article because no hysteresis effects were noted.

Spectral analysis
As a result of the solvothermal reactions, 1 and 5 were obtained (Supplementary Figures S1(a,b) and S2(a-c)). Considering that for the synthesis of 1, the pH of the reaction mixture was about 7, it was assumed that all of the carboxyl groups of BTC ligand were deprotonated [17a,b]. The FT-IR spectrum of 1 confirmed the deprotonation by the C ¼ O carbonyl asymmetrical and symmetrical (1721, 539 cm À1 ) BTC vibration bands decay [18]. On the other hand, the asymmetrical and symmetrical (1619, 1389 cm À1 for 1) COO À vibration bands of deprotonated carboxyl groups involved in the coordination of Tb 3þ were observed [10g,h, 18, 19]. The Tb 3þ ion coordination by BTC was also confirmed by the Tb-O vibration band (535 cm À1 ) [20]. The main evidence of heterocyclic L1 contribution to the formation of Tb(III) ion coordination compounds was the presence of two bands assigned to the stretching vibrations of C ¼ O in the FT-IR spectrum and characteristic proton shifts in the NMR spectrum (Supplementary Figure S3). Analysis of the FT-IR spectrum of L1 permitted identification of amide ($3230 cm À1 ) and methyl ester groups (3070-2848 cm À1 ) in this compound [12a]. The presence of Tb(III) ions in both components of 1 was also confirmed by SEM-EDS analysis (Supplementary Figure S4). In 1, 2 and 3, the central metal ions seem to be coordinated by the nitrogen donor atom from the pyridine ring of L1. Therefore, the C ¼ O vibration bands of the pyridinecarboxylic amide derivative are shifted insignificantly to 1714 and 1683 cm À1 for 1, 1714 and 1678 cm À1 for 2, and 1716 and 1689 cm À1 for 3 in comparison to their positions in the spectrum of L1 (1708, 1673 cm À1 ). A similar observation has been made for the methyl 2-amino-3methylbenzoatepyridine carboxamide derivative of pyridine-4-carboxylic acid [12b]. The FT-IR spectrum of 3 also displayed the presence of a thiocyanate group in the structure, evidenced by two bands at 2094 and 2083 cm À1 . This splitting of the cis-isomer structure of 3 along with the lower values of cm À1 speak for the N-bonded mode of the thiocyanate anion [19]. The FT-IR spectrum of 4 suggests the coordination of the central copper ion via one of the carbonyl groups because a strong shift of the characteristic stretching band to 1721 cm À1 was observed. In contrast to the spectrum of 3, the FT-IR spectrum of 8, apolymeric structure, demonstrated a single strong stretching band m(CN) at 2097 cm À1 . In fact the thiocyanate anion acts as a bridging linker between neighboring copper ions revealing both "end on" binding modes via N, N -SCN and S,S -SCN which have been confirmed by single-crystal X-ray diffraction analysis [21a,b]. Europium complex 5 with L2 was also synthesized by solvothermal methods. The high temperature and pressure conditions caused decomposition of the ester group to a carboxylic acid group in L2, which was also visible in the NMR spectrum (Supplementary Figure S3). It was found that the carbonyl and carboxyl groups took the lead in Eu(III) ion coordination [12a]. The SEM-EDS analysis of 5 (Supplementary Figure S4) also showed the coordination of Eu(III) by pyridinecarboxamide ligands via the oxygen and nitrogen donors in the vicinity of the central metal ion. The FT-IR spectrum of hybrid salt 6 shows insignificant shifts of carbonyl stretching bands in comparison to their positions in the spectrum of L2. The bands occurred at 1715 and 1688 cm À1 . These results are consistent with the single-crystal X-ray diffraction analysis which shows the ionic character of copper chloride [CuCl 4 À ] and protonated pyridine rings in L2. Copper ions in 7 and 8 are also coordinated by pyridine nitrogen donor atoms of L2 molecules (one finds more detailed comments about 4, 5, 7 and 8 in the Supplementary material). Supplementary Figure S5 presents a comparison of FT-IR spectra for selected compounds and substrates.
Since the Eu(III) and Tb(III) ions show interesting emission properties, luminescence properties studies were carried out for the coordination compounds obtained with lanthanide ions [22a,b]. The excitation spectrum of 1 was recorded at k obs =545 nm. Analysis of the emission spectrum of 1 (Figure 1) in comparison to the emission  Figure S6) at k ex =290, 300 nm indicated the presence of the energy transfer effect from the coordinated ligands to the central metal ions. The sensitized emission spectrum of 1 showed four main bands at 495, 545, 585 and 621 nm corresponding to the 5 D 4 -7 F 6 , 5 D 4 -7 F 5 , 5 D 4 -7 F 4 and 5 D 4 -7 F 3 transitions.
The excitation and emission spectra of 5 were recorded at k obs =620 nm and k ex =297 and 394 nm (filter 415 nm). The characteristic bands of the 5 D 0 level were observed at 5 D 1 -7 F 2 $558 nm, 5 D 0 -7 F 0 $581 nm, 5 D 0 -7 F 1 $594 nm, 5 D 0 -7 F 2 $618 nm, 5 D 0 -7 F 3 $653 nm and 5 D 0 -7 F 4 $697 nm (Figure 2). The efficiency of sensitized emission is reflected in the excitation spectrum which exhibited two maxima with comparable intensity (Supplementary Figure S7). The first band corresponds to the p-p Ã transition within the organic ligand. This band is characterized by a wide half-width and is located in the range from 240 to 320 nm. The narrow emission bands which occurred further in the spectral range were assigned to the Eu(III) f-f transitions. The 7 F 0 -5 L 6 transition at 394 nm exhibited the highest intensity. The leading character of the Eu(III) f-f transition in the system demonstrated ineffective energy transfer from the ligand to the europium ion. The chromaticity diagram (Supplementary Figure S8) shows the green and red color luminescence of 1 and 5, respectively.
The curves of 1 and 5 luminescence decay for the 5 D 4 -7 F 5 and 5 D 0 -7 F 2 transitions in solid state were recorded. The shape of decay curves of luminescence of 1 was approximated as a bi-exponential. For 1, the lifetimes reached about 221 and 833 ls. Supplementary Figure S9(a) in the Supplementary material presents a selected decay curve of 1's luminescence. The decay time of 5's luminescence is shown in Table 2 and Supplementary Figure S9 (b). The experimental data were fitted with R 2 =0.9980 using a single exponential function. The obtained lifetimes of Eu(III) and Tb(III) ions  correspond to those observed by us for the earlier studied systems [23a-d] and are in agreement with literature values [24a-c]. Because the luminescence lifetime of Ln(III) is very sensitive to the composition of the inner coordination sphere [25], the short lifetimes of 1 and 5 can be attributed to the presence of luminescence quenchers (H 2 O molecules) in the coordination spheres. The numbers of water molecules in 1 and 5 calculated from the Kimuras relations [26] were determined to be 4.0 and 3.6 (with an accuracy of 0.5 molecule). The obtained results indicate the presence of water molecules in the first coordination sphere of the metal ions as shown earlier.
The total decay rate is the sum of the rates of radiative (k rad ) and non-radiative (k nrad ) processes. The radiative lifetime (s rad ) of the 5 D 0 excited state of Eu(III) ion was calculated directly from its corrected emission spectrum using Equation (1): where A MD,0 is the spontaneous emission probability of the 5 D 0 -7 F 1 transition in vacuum (14.65 s À1 ) [27], n is the refractive index of the crystal (1, 5) and I tot /I MD is the ratio of the total area of the corrected Eu(III) emission spectrum to the area under the 5 D 0 -7 F 1 band.
On the basis of the recorded lifetimes of the 5 D 0 level, under direct excitation of Eu(III) combined with the radiation transitions rate constant value (A rad ), the rate constant of non-radiative transitions (A nrad ) was calculated, which determines the contribution of non-radiative processes to level 5 D 0 depopulation. As shown in Table 2, the total decay rate (A rad þA nrad ) of 5 D 0 level was dominated by the non-radiative component. This shows a large contribution of the non-radiative process to europium ion emission quenching.
The luminescence quantum yields for 1 and 5 were determined by measuring the quantum yield of the solid samples. The diffuse reflectance of the samples was determined relative to the non-absorbing standard KBr at excitation wavelengths 303 and 394 nm. Subsequently, the emission of the samples was measured in the same conditions. All procedures were carried out according to [23a, 28]. The luminescence quantum yields were calculated as 0.062 and 0.009 for 1 and 5, respectively.
Compounds 1 and 5 also showed good emission stability over time. The measurements were conducted for solid state samples for 3 h and an insignificant decrease in intensities was observed for both complexes (Supplementary Figure S9(c,d)).

Thermogravimetric analysis
The thermal stability of 1, 3, 4 and 5 was studied and the results are presented in Supplementary Figure S10. The compounds are stable in air at room temperature, but on heating they undergo decompositions along different pathways. Also, the TG analysis was carried out to establish the type of water molecules (lattice or coordination water) present in the obtained complexes. The water eliminated from the complexes below 423 K is the lattice water, while the water removed above this temperature is treated as coordination water to the central ion [29a,b].
Compound 1 was found to decompose in two steps. The first step is related to the release of three BTC molecules, three water molecules and four methyl ester groups from L1 per formula unit in the range of 175-476 C (Calcd: 40.81% and Found: 38.93%). After that the four remaining amide molecules without ester groups decomposed until 675 C (Calcd: 37.83%, Found: 35.17%). The molecule of terbium oxide remained after the complex decomposition.
For 3, the water molecule was removed at 190-219 C (Calcd: 2.44%, Found: 2.49%) and the compound decomposed in three steps. Afterwards the two SCN À anions were removed up to 267 C (Calcd: 15.73%, Found: 15.67%). The last decomposition molecules were two aromatic amine ester rings (268-742 C, Calcd: 44.48%, Found: 48.09%). The copper ion connected to two pyridine rings with carbonyl groups was left and not decomposed to the oxide.
The anhydrous complex 4 is stable to 200 C. Further heating (from 200 to 398 C) results in gradual decomposition of this complex. Subsequently the two chloride molecules and two molecules of aromatic amine ester rings were removed (Calcd: 59.15%, Found: 57.64%). Next the two pyridine rings decomposed up to around 740 C (Calcd: 31.44%, Found: 30.32%). Copper oxide was left after decomposition.
Thermogravimetric analysis showed that the water molecules in 1 and 3 are coordinatively linked to the central metal ion, while in 5 both lattice and coordination water molecules are present.

X-ray diffraction analysis
Supplementary Figure S11(a,b) present the juxtaposition of XRD patterns simulated from single-crystal analysis for 2, 6, 7, 8, L1, L2 and PXRD patterns for 1, 3, 4, 5 and BTC. In the pattern for the product of solvothermal synthesis (1), the reflections from both ligands are not observed at their characteristic 2-theta values. It was deduced that the white needle precipitate did not contain any unreacted substrate ligands and a new compound was formed from the reaction mixture [10d]. According to Hu et al. [30], the compounds with mixed-ligand structure consisting of BTC ligands can maintain similar framework topology even after incorporation of other aromatic ligand with approximate geometry, resulting in the unaffected PXRD pattern. The PXRD analysis of 3 revealed very low intensity signals. The air instability of this sample may be the reason for measurement disorders, consequently only two reflections were observed. Taking into account the results of earlier analyses of the spectra of complexes with other derivatives, the signals appeared at the positions characteristic of complexes with L1. The PXRD of 4 revealed the most intense, distinctive reflections and the diffractogram form was similar to that recorded for 2. Analysis of the PXRD patterns of complexes 5-8 and that of the substrate ligand L2 presented in Supplementary Figure S11b revealed significant shifts of the signals for all four compounds with L2. In view of the X-ray diffraction single-crystal data and FT-IR analysis, the differences in 5-8 diffractograms can be explained by multiple coordination modes of L2 and the presence of different anions coordinated to central metal ions. The PXRD powder diffraction measurements were compared with the simulated single crystal XRD diffractograms for 7 and 8 (Supplementary Figure S11(c)). Results of these measurements confirm that the powders have the same structure as the single crystals. Therefore, it indicates the high phase purity of obtained bulk materials [31a,b].
Single-crystal X-ray diffraction of 2 confirmed that Zn ion is four coordinate by two nitrogen atoms from two ligand molecules and two chloride ions (Figure 3). The coordination is close to tetrahedral (cf. Table 3). Differences in ligand conformations  Table 3. Relevant geometrical data for 2, 6, 7 and 8 (Å, ). A, B, C and D denote the mean planes of pyridine ring, C-CO-N-C fragment, phenyl ring and C-COOC fragment, respectively.  (14) 16.26 (16) can be related to the specific crystal packing and intermolecular interactions. The molecules are connected by N-HÁÁÁO hydrogen bonds (Table 4) into infinite chains along the y-direction, and these chains are interconnected and create the four-molecule rings which may be described (using graph-set notation) as R 4 4 (36), implying that in the 36-atom closed loop there are four hydrogen bond donors and four hydrogen bond acceptor atoms (Supplementary Figure S12). (The explanation for Alert B: Appendix A CIF alert explanation for complex 2).
For the three compounds obtained as a result of the reactions of L2 with copper chloride under various conditions, it was possible to get single crystals suitable for Xray structural analysis. Interestingly, their structures proved to be basically different.
The structure of 6 contains two protonated (at pyridine nitrogen atoms) L2 molecules and a CuCl 4 dianion, so basically this compound is a hybrid inorganic/organic salt. Additionally, there is a water molecule in the crystal structure, which takes part in determining the hydrogen bond architecture. In the anion, the copper(II) is four coordinate in a highly distorted tetrahedral fashion ( Figure 4). In the crystal structure, two organic moieties take part in the hydrogen bond network in different ways. Moiety A makes infinite chains with the help of a water molecule [C 2 2 (6) motif], while moiety B uses both hydrogen bond donors to create closed R 4 4 (22) rings with anions (two cations, two anions). These two basic motifs (Supplementary Figure S13) are interconnected by additional hydrogen bonds (waterÁÁÁanion, cation AÁÁÁanion), and all structural components are involved in a relatively complicated three-dimensional structure. (The explanation for Alert B: Appendix A CIF alert explanation for complex 6).
The structure of 7, at first sight, seems to be similar to that of 2: almost symmetrical, CuCl 2 (L2) 2 complexes with four-coordinate metal ions; however, the coordination mode of the metal cation is completely different in these two complexes. In 7, the coordination mode defines a quite regular, square-planar geometry ( Figure 5). The intermolecular interactions are also different. The N-HÁÁÁCl and N-HÁÁÁO hydrogen bonds close the sequential, centrosymmetric R 2 2 (18) and R 2 2 (38) rings (Supplementary Figure S14).
In 8, the basic structure is similar to that of 7: C s -symmetrical Cu(NCS) 2 (L2) 2 complexes with square-planar central Cu cations (Cu and NCS ligands lie in the mirror planes). However, longer, but still capable of bonding, Cu-S(x,y,1 þ z) bonds (2.8409(16) Å) connect these building blocks into infinite, one-dimensional coordination polymers ( Figure 6). Taking these weaker bonds into account, the Cu ion is five coordinate, and the coordination polyhedron is a regular square pyramid. Neighboring polymers are connected by N-HÁÁÁO hydrogen bonds (Supplementary Figure S15).

Magnetic properties
Magnetic measurements were carried out for 1, 3, 4, 7 and 8. No monocrystal of 1 was obtained. Thus for 1, only the temperature dependence (2-300 K) of the gram magnetic susceptibility was analyzed. As follows from this dependence, Tb(III) complex has paramagnetic properties and obeys the Curie-Weiss law. The gram magnetic susceptibility value decreases with temperature increasing from about 1.20 Â 10 À3 at 2 K to 0.6 Â 10 À4 (cm 3 /g) at 299 K (Supplementary Figure S17). Since the molecular structure of this complex was not determined, the diamagnetic and structural corrections were not calculated. However, taking into account only selected segment of this complex polymer we tried to estimate the spatial framework of this compound on the basis of the determined magnetic moments. Including the diamagnetic and structural corrections, it was possible to determine the magnetic moment values. For this purpose, Pascal's constants were used. The magnetic moment values for Tb(III) complex changed from 6.22 lb (2 K) to 16.55 lb (299 K). Having these values, it was possible to deduce its presumable structure as a trimer. The magnetic moment increase was probably caused by electron transition from ligand BTC oxygen anion p orbitals into Figure 6. Fragment of the coordination polymer observed in the structure of 8; ellipsoids are drawn at the 50% probability level and hydrogens are shown as spheres of arbitrary radii. 6s and 5d Tb(III) ion orbitals. Therefore it was deduced that the BTC oxygen donor atoms and L1 pyridine nitrogen atoms take part in the Tb(III) ion coordination. Figure 7 shows temperature dependence of the magnetic susceptibility v M (T) (left axis) for 7. The right axis corresponds to the dependence of v M T on T. The large peak visible at low temperatures may result from the presence of relatively strong antiferromagnetic interactions. Indeed, it is confirmed if the magnetic data are analyzed using the magnetic susceptibility equation for the spin S= 1 = 2 including the correction of the molecular field and the temperature-independent paramagnetism (TIP) [33]: where g is the spectroscopic splitting factor, N is the Avogadro's number, b the Bohr magneton, k the Boltzmann constant, zJ 0 intermolecular exchange parameter and z is the number of the nearest neighbors of Cu 2þ center. This Curie-Weiss type analysis for temperature range above the peak provides the following values of the parameters: g ¼ 2.1, zJ 0 = À17.5 cm À1 , and TIP = 24.7 Â 10 À4 cm 3 /mol. This negative exchange strength indicates antiferromagnetic type of interactions between Cu ions. The maximum in v M (T) can be modeled on the basis of the Bleaney-Bowers equation for dimeric system [34]: where J is the exchange parameter. In Figure 7, the plot according to Eq. (4) is shown as the dashed line, however it provides unreasonable g value (g ¼ 1.9), therefore it is often preferred to fit v M T as a function of T, which increases the weight of the high temperature data points. Such an analysis (right axis) results in g ¼ 2.0, J= À7.4 cm À1 and TIP = 26.2 Â 10 À4 cm 3 /mol. The linear increase in v M T with temperature above 50 K is due to TIP-if one plots (v M T-TIP) versus T, the expected saturation (Curie behavior) is observed ( Figure 7) and at 300 K the value (v M T-TIP)=0.365 cm 3 K/mol agrees well with the theoretically expected value of 0.374 cm 3 K/mol for spin 1 = 2 (Cu 2þ ), which corresponds to the effective magnetic moment of 1.73 M.B. (Bohr magnetons). Alternatively, assuming the singlet ground state, one can test the expression for interacting spin dimers of spin 1 = 2 [35a,b]: where D is a spin gap between the singlet ground state and triplet excited states and is a measure of the intra-dimer exchange coupling. J 0 is the average inter-dimer exchange coupling. The corresponding fit is presented in Supplementary Figure S18, as the dotted line and the obtained values of parameters are g ¼ 2.14, D ¼ 12.2 K, J 0 =27 K and TIP = 25 Â 10 À4 cm 3 /mol. It implies that both types of the exchange coupling may be relevant in the complex studied. The presence of antiferromagnetic interactions in 7 is confirmed by the measurements of magnetization curves. As shown in Supplementary Figure S19, after an initial linear increase, a rapid growth of magnetization occurs above the magnetic field m 0 H$4 T. It is typical of rotation of the spins followed by a metamagnetic-like transition at appropriate magnetic field.
For 8, a different behavior is found ( Figure 8); there is no maximum in the magnetic susceptibility and Eq. (2) provides g ¼ 2.08, zJ 0 = À0.61 cm À1 and TIP = 49 Â 10 À4 cm 3 /mol. The Bleaney-Bowers equation leads to the parameters g ¼ 2.01, J= À0.2 cm À1 and TIP = 51 Â 10 À4 cm 3 /mol. In each case, it is obvious that the interactions are negligible in this complex, but the temperature-independent contributions are large. The weak interactions can be also concluded from the magnetization curve  (inset of Figure 8), whose shape indicates a typical paramagnetic behavior is visible in accordance with the Brillouin function.
Supplementary Figure S20 presents magnetometric results for 3. This complex appeared sensitive to ambient conditions and partial degradation of the sample could be noticed, therefore the experimental data have followed neither the Curie-Weiss nor the Bleaney-Bowers model. The v M (T) dependence could be approximated only by the Bleaney-Bowers model modified by including a term resulting from the presence of a paramagnetic impurity [36]: where X is a fraction of the impurity assumed to have a comparable molecular weight. The fit gives J= À5.5 cm À1 , TIP = 7.9 Â 10 À4 cm 3 /mol and X ¼ 7%. To reduce the number of free parameters, g=g i =2.0 was assumed. Hence, the value of the exchange interaction strength is probably intermediate between those for 7 and 8. The magnetization curve (inset of Supplementary Figure S20) resembles that obtained for paramagnetic 8.
Measurements of the magnetic parameters for 4 lead to similar conclusions as for 7. The solid line in Supplementary Figure S21 is obtained with Eq. (2) for parameters g ¼ 2.
1, zJ 0 = À16.7 cm À1 , and TIP = 24 Â 10 À4 cm 3 /mol. The dotted line illustrates the fit with Eq. (5) which implies the following values of the parameters: g ¼ 2.12, D ¼ 6.9 K, J 0 =35 K and TIP = 25 Â 10 À4 cm 3 /mol, similar to the values obtained for 4. Therefore, like for 7, the coupling is relatively strong and of antiferromagnetic type, which is also confirmed by the magnetization curve (inset of Supplementary Figure S21) illustrating a metamagnetic-like behavior. The accessible magnetic field of 9T is too small to run the system through the metamagnetic transition (transition from the non-collinear AFM-type order to parallel alignment of the magnetic moments), but with much higher saturation of magnetic field a higher magnetic moment value can be expected.
The analysis with the Bleaney-Bowers equation is displayed in Supplementary Figure S22 and the solid line is a fit providing g ¼ 2.0, TIP = 0 and J= À6.06 cm À1 .
Considering the magnetic measurement results in reference to the obtained or predicted structures of complexes, the compounds obtained showed similar magnetic behavior. Going into detail, copper(II) complexes 4 and 7 with two different amide ligands have adopted similar coordination environments including two ligands and two anchored chloride anions on the central metal ions. This may be the reason for the antiferromagnetic interaction in both compounds. In complexes 3 and 8, the thiocyanate anion presence in the inner coordination sphere becomes a common feature for both compounds. The paramagnetic properties of the complexes studied are in good correspondence with the predicted composition of these complexes. On the other hand, the exchange interaction strength for 3 is intermediate between 7 and 8. This may reflect the different coordination mode of thiocyanate anion, which creates 1D chain coordination polymer structure 8 or a single complex structure 3.

Conclusion
Eight new complexes and self-assemblies constructed with two amide derivatives of pyridine-4-carboxylic acid have been synthesized by the solvothermal and one pot method and structurally characterized. We conclude that the ligands are coordinated to metal ions via N pyridine and O carboxyl group. The solvothermal synthesis allowed obtaining ternary self-organized structures with BTC and amide ligand L1. For the thiocyanate anion, the bridging and monodentate N-bonded coordination modes were established in Cu(II) assemblies. The photoluminescence behaviors of 1 and 5 have been characterized by emission, luminescence lifetimes and quantum yields measurements in the solid state at room temperature. A large contribution of the non-radiative process in quenching of europium ion emission was evidenced. Compounds 2, 6, 7 and 8 were characterized by single crystal analysis. The N-HÁÁÁO hydrogen bonds played an important role in the packing of these crystals. The magnetic behavior of obtained complexes can be inferred as antiferromagnetic interactions between metal centers in 4 and 7 and paramagnetic in 1, 3 and 8.