A (U)MP2(full) and (U)CCSD(T) theoretical investigation into the substituent effects on the intermolecular T-shaped F-H center dot center dot center dot pi interactions between HF and LBBL (L = -H, :CO, :NN, -Cl, -CN and -NC)
The substituent effects on the intermolecular T-shaped F-HaEuro broken vertical bar pi interactions are investigated between HF and LBBL (L = -H, a CO, :NN, -Cl, -CN and -NC) using the (U)MP2(full) and (U)CCSD(T) methods with the 6-311++G(2 d,p) basis set. The B a parts per thousand B triple-bond contraction is found in the complexes with lone-pair-electron donors while the B = B double-bond is lengthened in the systems with the single-electron substituents upon complexation. The T-shaped F-HaEuro broken vertical bar pi interaction energies follow the order of ClB = BClaEuro broken vertical bar HF > HB = BHaEuro broken vertical bar HF > NNB a parts per thousand BNNaEuro broken vertical bar HF > OCB a parts per thousand BCOaEuro broken vertical bar HF > CNB = BNCaEuro broken vertical bar HF > NCB = BCNaEuro broken vertical bar HF. The electron-donating substituents a CO and :NN increases electron density of the B a parts per thousand B triple bond by the delocalization interaction E ((2)) pi ((CO/NN)-> Lp(B)) while the electron-withdrawing substituents -CN and -NC decrease electron density of the B = B double bond by means of the pi-pi conjugative effect. The analyses of the APT atomic charge, "truncated" model, natural bond orbital (NBO), atoms in molecules (AIM) and electron density shifts reveal the nature of the substituent effect and explain the origin of the B a parts per thousand B bond contraction.
substituent effect "truncated" model bb multiple bond intermolecular t-shaped h center dot center dot center dot pi interaction