Synthesis, crystal structure, and DFT study of two new dinuclear copper(I) complexes bearing Ar-BIAN ligands functionalized with NO2 groups

Acknowledgments : This work was supported by the Associate Laboratory for Green Chemistry- LAQV financed by national funds from FCT/MCTES (UIDB/50006/2020). M. J. C. and M. O. acknowledge the Fundação para a Ciência e a Tecnologia (FCT) for support (UIDB/04046/2020 and UIDP/04046/2020). The authors acknowledge LabRMN at FCT-UNL and Rede Nacional de RMN (RNRMN) for access to the facilities. The NMR spectrometers are part of The National NMR Facility, supported by FCT (ROTEIRO/0031/2013 - PINFRA/22161/2016) (co-financed by FEDER through COMPETE 2020, POCI, and PORL and FCT through PIDDAC). Data Mass Spectrometry obtained by the Laboratório de Análises/LAQV REQUIMTE - Chemistry department FCT University NOVA of Lisbon. The SCXR determinations were performed in house (equipment financed by national funds through project RECI/BBB-BEP/0124/2012 from FCT/MCTES). S. B. acknowledges project SmartBioR for financial support (CENTRO-01–0145-FEDER-000018, Integrated Programme SR&TD co-funded by Centro 2020 program, Portugal 2020, European Union, through the European Regional Development Fund). M. O. acknowledges PhD Grant SFRH/BD/120985/2016 financed by FCT.

Two new bis(aryl-imino)-acenaphthene, Ar-BIAN (Ar = 2,4,6-trimethylphenyl = mes) ligands, bearing the NO2 group in the naphthalene moiety of the iminoacenaphthene at para- (5-NO2) and meta- (4-NO2) position, of formulations 1,2-bis(mes-imino)-5-nitroacenaphthene, 1, and 1,2-bis(mes-imino)-4-nitroacenaphthene, 2, were synthesized. Their respective dinuclear iodide bridged copper(I) complexes [Cu2(μ-I)2(mes-BIAN-5-NO2)2], 3 and [Cu2(μ-I)2(mes-BIAN-4-NO2)2], 4, were obtained in good yields by treatment with an equimolar amount of CuI. All compounds were characterized by elemental analysis, single-crystal X-ray diffraction, 1H-NMR, 13C-NMR, FTIR, UV/Vis spectroscopy. DFT calculations helped to understand the different molecular structure observed in the crystals of 3 and 4 and the determining role of packing forces. TDDFT revealed that the absorption bands in the visible were essentially MLCT (Metal to Ligand Charge Transfer), with some n→π* character (intra ligand). The shift to the red compared to the spectrum of the Cu(I) complex analogue without the NO2 group, [Cu2(μ-I)2](mes-BIAN)2], 6, could be explained by the stabilization of the ligand unoccupied π* orbitals in the presence of NO2.

info:eu-repo/semantics/publishedVersion