Supramolecular association in Cu(II) coordination complexes involving energetically significant NO⋯NO π–hole interaction and cooperative π-stacked ternary assembly: Experimental and theoretical studies

Abstract

Two new copper (II) coordination solids involving 1,10-phenanthroline (phen) and benzoate (bz) viz., [Cu(phen)(H2O)2(η2-NO3)]·NO3 (1) and [Cu(phen)2(η2-bz)]·2bzH·NO3 (2) [bzH = benzoic acid] have been synthesized and characterized by X-ray crystal structure analysis, FT-IR, electronic spectra, ESR and TGA. Theoretical calculations have been performed to analyse some unconventional non-covalent interactions observed in the solid state structures of compounds 1 and 2. In compound 1, 1D supramolecular chain is formed between the cationic moieties through the anti-parallel NO⋯NO π–hole interactions involving the coordinated nitrato co-ligands which have been scarcely describe in the literature. The NCI plot analysis reveals the existence of the anti-parallel NO⋯NO π–hole interaction for the supramolecular dimer of compound 1. The binding energy of the NO⋯NO π–hole interaction in the supramolecular dimer is −18.2 kcal/mol, thus, indicating a moderately strong interaction. In compound 2, a remarkable cooperative (π–π)2/(π–π)1/(π–π)2 type network for self-assembly progression of the ternary π-stacked assembly has been studied. The computation of the energetic features reveals that (π–π)1 is reinforced by the presence of (π–π)2 in compound 2. The microbial activities have been investigated for both the compounds.