Spectroscopic characterization of non-covalent CuPc-GO system. Experiment and theory

Abstract In this study we report on UV-vis, IR and Raman studies of non-covalent copper phthalocyanine (CuPc) – flake graphene oxide (GO) complex in water and in the solid phase. Experimental results were supported by molecular modeling of structure, electronic and vibrational parameters for free CuPc and its 1 : 1 complexes with water, benzene, phenol, neutral and deprotonated benzoic acid. HOMO-LUMO gaps for these complexes were calculated and compared with data derived from the absorption edge of Q-band in the recorded UV-vis spectra for free CuPc and its adduct with GO in water. Small but non-negligible changes in position of spectral bands observed as result of CuPc interaction with GO were consistent with theoretical models predicted by density functional theory (DFT). Both the observed spectroscopic changes and theoretical shifts of spectral bands supported a direct interaction between CuPc and GO. The interaction site of CuPc was copper ion - small molecules were bound preferably to Cu2+ and its vicinity as an additional axial ligand forming a kind of T-shaped structure. In case of benzene and phenol sandwich type complexes were formed.