Effect of the Substitution Pattern (Peripheral vs Non-Peripheral) on the Spectroscopic, Electrochemical, and Magnetic Properties of Octahexylsulfanyl Copper Phthalocyanines Tulin Ates ̧ Turkmen, † Lihan Zeng, ‡ Yan Cui, ‡ I ̇ smail Fidan, § Fabienne Dumoulin,* ,§ Catherine Hirel, § Yunus Zorlu, §,△ Vefa Ahsen, § Alexander A. Chernonosov, ∥ Yurii Chumakov, †,⊥ Karl M. Kadish,* ,‡ Ays ̧ e Gü l Gü rek,* ,§ and Sibel Tokdemir O ̈ ztü rk* ,† † Department of Physics, § Department of Chemistry, and △ Institute of Nanotechnology, Gebze Technical University, 41400 Gebze, Kocaeli, Turkey ‡ Department of Chemistry, University of Houston, Houston, Texas 77204-5003, United States ∥ Institute of Chemical Biology and Fundamental Medicine, 8 Lavrentiev Avenue, Novosibirsk 630090, Russia ⊥ Institute of Applied Physics of the Academy of Sciences of Moldova, Academiei strasse 5, Chisinau, Moldavia *S Supporting Information ABSTRACT: In 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) cm 3 ·K/mol and −23 × 10 −5 (25 × 10 −5 ) cm 3 /mol respectively for Cu-P and Cu-NP. The room temperature magnetic moment value (1.70 μ B ) is close to the spin-only value (1.73 μ B ) for the peripheral complex, showing that there is no orbital contribution to μ eff . In contrast, at room temperature, the value of the magnetic moment (1.77 μ B ) 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). 1. INTRODUCTION Phthalocyanines (Pcs) are molecular materials exhibiting properties exploited in various applications, such as pigments in paints and printing inks, IR security devices, information storage and computer disk writing, or photodynamic therapy of cancer. 1 Many of these applications are based on the spectroscopic, electronic, and/or photochemical properties of the compounds. The nature, position, number, and even bulkiness of the substituents on the Pcs, as well as the nature of the metal and possible axial substituents, are structural factors known to affect these properties. 2 Most Pcs have a square- planar structure, 3 promoting intermolecular interactions, such as aggregation, liquid crystallinity, or specific packing. Numerous applications benefit from the Pcs’ maximum absorption commonly centered at ∼700 nm, and efforts have been made to further red-shift this band. In addition to providing an extension of the electronic delocalization in the Received: February 28, 2018 Article pubs.acs.org/IC Cite This: Inorg. Chem. XXXX, XXX, XXX-XXX © XXXX American Chemical Society A DOI: 10.1021/acs.inorgchem.8b00528 Inorg. Chem. XXXX, XXX, XXX−XXX