Cation-π-complex of Ag(I) ion with 1H-indole-5-carboxylic acid – Structural analysis and energetics of the M–L bonds

Abstract

Abstract This paper aims at filling the gap of governing forces leading to bonded charged AgI–ion to unsaturated hydrocarbons comparing with its coordination ability in metal–organics, in particular, carboxylic acids, describing a new, first reported in the literature, very rare case of cation-π–complex of AgI–ion with 1H-indole-5-carboxylic acid ([AgI(η2-C9H7NO2)3(NO3)]) (1). Correlation between bonding fusion of AgI–ion, examining four interaction modes (π–complex to ethene fragment (I); π–complex to phenyl fragment (II); M–N bond formation (III); and M–O bond formation (IV)) and the energetics of the interacting complex system is carried out. The energetics of M–L bonds is studied using topologic charge density analysis at bond critical points (bcps) using experimental crystallographic electron densities. The bond energies are correlated to theoretical quantum chemical bond dissociation energies. The methods of single crystal X-ray diffraction and computational quantum chemistry such as ‘atoms in molecules’ (AIM); ‘natural bond orbital analyses’ (NBO) and electrostatic potentials are used. The research takes dual steps associated with: (i) increasing the understanding about the molecular forces causing for preferred cation-π–interactions of AgI–ions even in presence of classical ligand like a carboxylic acid; and (ii) provides a thermodynamic explanation about bonding affinity of AgI–ion towards polydentate molecular systems. Clearly then, the paper has fundamental importance for the organometallic and inorganic chemistry. Owing the great significance of the cation-π–interactions in the folding of proteins; neurological signaling in living cells, and many more phenomena in the biological systems, our paper also has an underlined interdisciplinary impact.