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Hydrogen-Bonded Supramolecular Architectures of Organic Salts Based on Aromatic Tetracarboxylic Acids and Amines

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journal contribution
posted on 01.11.2006, 00:00 by Jian-Rong Li, Ying Tao, Qun Yu, Xian-He Bu
Crystallizations of two aromatic tetracarboxylic acids, 1,4,5,8-naphthalenetetracarboxylic acid (H4NTA) and 3,4,9,10-perylenetetracarboxylic acid (H4PTA), with amines (triethylamine, TEA; ethylenediamine, EDA) in H2O give four H-bonded organic salts, [HTEA]2·[H2NTA]·2H2O (1), [HTEA]2·[H2PTA] (2), [H2EDA]2·[NTA]·3H2O (3), and [H2EDA]2·[PTA]·8H2O (4), which were structurally characterized by X-ray diffraction. In the TEA salts (1 and 2), two protons of each acid are transferred and the supramolecular H-bonded entities are generated by only acid anions (or together with H2O), whereas in 3 and 4 all four protons are transferred and both H2EDA2+ and acid anions contribute to the final framework formation, probably due to the differences in basicities of the two amines. Salt 1 has a layer structure stabilized by O−H···O H-bonds between H2O and H2NTA2- and contains a normal graph set of R24(8) (formed by two H2O and two carboxyl O atoms). Different from 1, 2 contains a 1-D structure with an R22(16) ring formed by O−H···O H-bonds between H2PTA2-. Both 3 and 4 have 3-D framework structures with well-defined 1-D channels, assembled by complicated N−H···O and O−H···O H-bonds. All the O and amino H atoms in H2EDA2+ and NTA4- or PTA4- participate in the H-bonding linkages; however both salts have great structural differences with different numbers of cocrystallized H2O. It is interesting that the 1-D channels in 3 are circular and occupied by single H2O line but those in 4 are rectangular and filled by H2O tapes with a T4(2)6(2) pattern. Herein, TEA with a larger volume and simple H-bonding manner is considered as a terminal H-bonding moiety to form low-dimensional networks, whereas EDA with favorable flexibility and various H-bonding modes is adopted to link the acid components to give higher dimensional frameworks. In addition, H4PTA seems to be proven as an interesting H-bonding molecular tecton with great potential in crystal engineering, especially for preparing materials with large cavities/channels. The stability and luminescent property of 4 have also been studied preliminarily.