Host-guest interaction studies of polycyclic aromatic hydrocarbons (PAHs) in alkoxy bridged binuclear rhenium (I) complexes

The interaction of two neutral alkoxy bridged binuclear rhenium(I) complexes, 1 and 2 [{Re(CO)3(1,4-NVP)}2(μ2-OR)2] (1, R = C4H9; 2, R = C10H21; 1,4-NVP = 4-(1-naphthylvinyl)pyridine] with polycyclic aromatic hydrocarbons (PAH) is investigated. UV–vis absorption, emission, 1H NMR spectral titrations, TCSPC lifetime studies and DFT theoretical calculations were carried out to examine the binding responses of complexes 1 and 2 with various PAHs such as pyrene, naphthalene, anthracene and phenanthrene. The UV–Vis absorption spectra showed an increase in absorbance of the metal-to ligand charge-transfer (MLCT) and ligand centered (LC) bands upon addition of various PAH molecules to 1 and 2, whereas the emission behavior was found to show emission quenching, which might occur through energy transfer pathway. The binding constants (K) of complexes 1 and 2 for various PAHs are found to be in the order of 104 M−1 with a 1:1 binding mode, as determined from UV–vis absorption and emission spectral titration studies. 1H NMR spectral studies show that the chemical shifts of pyrene guest and the 1,4-NVP moiety of 2 are shifted up-field, whilst the alkoxy protons do not show any appreciable change in their chemical shifts. It is believed that the open cavities present in the Re(I) complexes may lead to the recognition of PAHs via CH···π interaction. Alkoxy bridged binuclear rhenium(I) complexes as a host for polycyclic aromatic hydrocarbons (PAHs) and the formation of Host-Guest complexes through CH···π interactions. [Display omitted] •Alkoxy bridged binuclear rhenium(I) complexes as a host for polycyclic aromatic hydrocarbons (PAHs)•Aromatic hydrocarbons quenches the luminescence of Re(I) complexes.•Host-Guest complex formation between aromatic hydrocarbons with Re(I) complexes through CH···π interactions