Strong N−X⋅⋅⋅O−N Halogen Bonds: A Comprehensive Study on N‐Halosaccharin Pyridine N‐Oxide Complexes.

Puttreddy, Rakesh; Rautiainen, J. Mikko; Mäkelä, Toni; Rissanen, Kari

A study of the strong N−X⋅⋅⋅−O−N (X=I, Br) halogen bonding interactions reports 2×27 donor×acceptor complexes of N‐halosaccharins and pyridine N‐oxides (PyNO). DFT calculations were used to investigate the X⋅⋅⋅O halogen bond (XB) interaction energies in 54 complexes. A simplified computationally fast electrostatic model was developed for predicting the X⋅⋅⋅O XBs. The XB interaction energies vary from −47.5 to −120.3 kJ mol−1; the strongest N−I⋅⋅⋅−O−N XBs approaching those of 3‐center‐4‐electron [N−I−N] halogen‐bonded systems (ca. 160 kJ mol−1). 1H NMR association constants (KXB) determined in CDCl3 and [D6]acetone vary from 2.0×100 to >108 m−1 and correlate well with the calculated donor×acceptor complexation enthalpies found between −38.4 and −77.5 kJ mol−1. In X‐ray crystal structures, the N‐iodosaccharin‐PyNO complexes manifest short interaction ratios (RXB) between 0.65–0.67 for the N−I⋅⋅⋅−O−N halogen bond.

HALOGENS; PYRIDINE; BINDING constant; CRYSTAL structure; ACETONE

Angewandte Chemie, 2019, Vol 131, Issue 51, p18783

0044-8249

Academic Journal

10.1002/ange.201909759