P⋯N type pnicogen bonding in phosphorus trichloride–pyridine adduct: A matrix isolation infrared, DFT and ab initio study

• Published in: Journal of molecular structure Vol. 1217; p. 128408
• Main Authors: Joshi, Prasad Ramesh, Sankaran, K.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 05-10-2020
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/j.molstruc.2020.128408

Matrix isolation infrared spectroscopy in low temperature N2 matrices with the support of Density Functional Theory (DFT) and ab initio computations have been employed to investigate noncovalent forces formed between phosporous trichloride (PCl3) and hetero cyclic Pyridine (C5H5N) molecules. The possible geometries of PCl3–C5H5N adducts were optimized by computations performed at B3LYP/6–311++G(d,p) and MP2/6–311++G(d,p) levels of theory. Two minima, a global minimum and a local minimum, on the potential energy surface have been obtained for PCl3–C5H5N adduct system and the main force of interaction for their stabilization is pnicogen bonding (phosphorus bonding). The global minimum is stabilized by Cl–P⋯N interaction whereas local minimum is stabilized by Cl–P···π interaction. Interestingly, experiments revealed large red shift of 48.5 cm−1 for P–Cl stretching vibrational mode (ν3) in N2 matrix and this magnitude of shift is in good agreement with computational shift for PCl3–C5H5N adduct which is stabilized by Cl–P⋯N interaction. Moreover, computations predicted that P⋯N interacting adduct is stronger than the P···π interacting adduct by 2.02 kcal/mol at MP2/6–311++G(d,p) levels of theory. To understand the nature of interactions and the effect of charge transfer interaction on the stability of the adducts, Atoms In Molecules (AIM) and Natural Bond Orbital (NBO) analysis were performed.
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•Study of pnicogen bonding (noncovalent interaction force) in PCl3–C6H5N system using matrix isolation infrared spectroscopy.•Experimental evidence of P⋯N type of interaction in PCl3–C6H5N system.•AIM and NBO analyses accomplished to comprehend then nature of interactions in the adducts.