ic8b00528_si_001.pdf (1.77 MB)
Effect of the Substitution Pattern (Peripheral vs Non-Peripheral) on the Spectroscopic, Electrochemical, and Magnetic Properties of Octahexylsulfanyl Copper Phthalocyanines
journal contribution
posted on 2018-05-16, 11:20 authored by Tulin Ateş Turkmen, Lihan Zeng, Yan Cui, İsmail Fidan, Fabienne Dumoulin, Catherine Hirel, Yunus Zorlu, Vefa Ahsen, Alexander A. Chernonosov, Yurii Chumakov, Karl M. Kadish, Ayşe Gül Gürek, Sibel Tokdemir ÖztürkIn
order to investigate the substitution position effect on the spectroscopic,
electrochemical, and magnetic properties of copper phthalocyanines,
a detailed structure–property analysis has been performed by
examining two copper phthalocyanines that are octasubstituted by hexylsulfanyl
chains respectively in the peripheral (Cu-P) and non-peripheral
(Cu-NP) positions. Cu-NP showed a marked
near-IR maximum absorption compared to Cu-P and, accordingly,
a smaller HOMO–LUMO energy gap, calculated via the electrochemical
results and simulations in the gas phase, as well as for Cu-NP from its crystallographic data. An electron-spin resonance (ESR)
technique is used to extract the g values from the
powder spectra that are taken at room temperature. The g values were determined to be g∥ = 2.160 and g⊥ = 2.045 for Cu-P and g∥ = 2.150 and g⊥ = 2.050 for Cu-NP. These
values indicate that the paramagnetic copper center in both phthalocyanines
has axial symmetry with a planar anisotropy (g∥ > g⊥). The ESR
spectra in solution could be obtained only for Cu-P.
Curie law is used to fit the experimental data of the magnetic susceptibility
versus temperature graphs, and the Curie constant (C) and diamagnetic/temperature-independent paramagnetic (α)
contributions are deduced as 0.37598 (0.39576) cm3·K/mol
and −23 × 10–5 (25 × 10–5) cm3/mol respectively for Cu-P and Cu-NP. The room temperature magnetic moment value (1.70 μB) is close to the spin-only value (1.73 μB) for the peripheral complex, showing that there is no orbital contribution
to μeff. In contrast, at room temperature, the value
of the magnetic moment (1.77 μB) is above the spin-only
value, showing an orbital contribution to the magnetic moment. Cu-NP’s room temperature magnetic moment value is larger
than the value for Cu-P, demonstrating that the orbital
contribution to the magnetic moment depends upon the substituent position.
The magnitudes of the effective magnetic moment values also support
that both Cu-P and Cu-NP complexes have
square-planar coordination. This result is consistent with the determined g values. The spin densities were determined experimentally,
and the results suggest that the positions of the substituents affect
these values (0.469 for Cu-P and 0.490 for Cu-NP).