Synthesis and detailed structural characterization of a new coordination compound [Ni(NCS)2L]∙3MeOH, synthesised from a mixture of Ni(NO3)2 and NaNCS with a bulky helical organic ligand 1,2-diphenyl-1,2-bis((phenyl(pyridin-2-yl)methylene)hydrazono)ethane (L) in MeOH, is reported. The metal is tetracoordinated by ligand L with its 12 π electron chelate ring via the pyridyl-imine units and completes its coordination sphere with two N-bound thiocyanate anions to form the mononuclear [Ni(NCS)2L] complex that adopts a quasi-aromatic Möbius metal chelate structure. Crystal packing of [Ni(NCS)2L]·3MeOH is stabilized by intermolecular O–H∙∙∙S and O–H∙∙∙O hydrogen bonds, intra- and intermolecular C–H∙∙∙π interactions as well as by intermolecular C–S∙∙∙π interactions. The Hirshfeld molecular surface of [Ni(NCS)2L] is dominated by highly favoured H∙∙∙X (X = C, N, O and S) contacts as well as by far less favoured H∙∙∙H contacts. The Kubelka-Munk based absorption spectrum of [Ni(NCS)2L]·3MeOH exhibits bands in the UV region, corresponding to intraligand π → π* and/or n → π* transitions, bands in the visible region, arising from metal-to-ligand charge transfers from both the organic ligand L and thiocyanate anions, as well as from the spin allowed d–d transitions 3A2g → 3T1g (3P), 3A2g → 3T1g (3F), 3A2g → 3T2g and 3A2g → 1Eg transitions. Finally, theoretical DFT calculations have been performed to analyze an unconventional H3C⋯π(C=S) interaction between the co-crystallized MeOH molecule and the thiocyanate ligand that can be classified as a σ-hole carbon bonding interaction with an electron transfer from the π-system of NCS to the antibonding C–O sigma orbital, π(NCS) → σ*(C–O).
