Interaction Energies and NMR Indirect Nuclear Spin−Spin Coupling Constants in Linear HCN and HNC Complexes

Abstract

The cooperativity effects on both the electronic energy and NMR indirect nuclear spin-spin coupling constants J of the linear complexes (HCN)n and (HNC)n (n = 1-6) are discussed. The geometries of the complexes were optimized at the MP2 level by using the cc-pVTZ basis sets. The spin-spin coupling constants were calculated at the level of the second-order polarization propagator approximation with use of the local dense basis set scheme based on the cc-pVTZ-J basis sets. We find strong correlations in the patterns of different properties such as interaction energy, hydrogen bond distances, and spin-spin coupling constants for both series of compounds. The intramolecular spin-spin couplings are with two exceptions dominated by the Fermi contact (FC) mechanism, while the FC term is the only nonvanishing contribution for the intermolecular couplings. The latter do not follow the Dirac vector model and are important only between nearest neighbors.

Understanding NMR J‐couplings by the theory of polarization propagators

“…Shall there be cooperativity effects on their NMR spectroscopic parameters? The analysis of inter-and intramolecular J-couplings shows that the answer is affirmative (123). One should look for a new way to quantify cooperativity effects on local magnetic properties.…”

“…The analysis of the energetics for the linear chains (HCN) n and (HNC) n (n ¼ 1À6) (123,124) shows that these chains have important cooperativity effects. They are observed in the length of all hydrogen bonds which are shortened as the size of the cluster increases (125).…”

Non‐empirical calculations of NMR indirect carbon–carbon coupling constants. Part 10—Carbocages

“…Based on our previous results, 1 -9 in the calculations of J(C,H) we used cc-pVXZ-Cs (X D D,T) basis sets augmented with inner core s-functions of Woon and Dunning 85 for coupled carbons and aug-cc-pVTZ-J with tight s-functions of Provasi et al 93 for coupled hydrogens.…”

Dihydrogen bond cooperativity in (HCCBeH)n clusters

“…[17][18][19] There are very few other possibilities. One of them, based on DHBs, is schematized in Scheme 1͑b͒.The system chosen in the present article, HC ϵ CBeH, has the HB donor and acceptor groups in both extremes of the molecule and based on these characteristics can be considered an analog of HCN and HNC.…”

“…The hydrogen bonded clusters of HCN can be obtained in linear or cyclic dispositions and have shown to present cooperativity effects that have been characterized experimentally and theoretically. 4,[18][19][20] The HCCBeH molecule has been experimentally described in the laser ablation of acetylene with beryllium and characterized based on the IR spectra and density functional theory ͑DFT͒ calculations ͓B3LYP/ 6-311G͑d͔͒. 21 …”