Theoretical Studies Of Weak Interactions Between Halogenated Five/Six-heterocyclic Compounds And Small Molecules

Weak interactions between halogenated five or six membered heterocyclic compounds and small molecules have become a hot research area in chemistry field.Weak interactions including lp(lone pair)…π,halogen bond and hydrogen bond between halogenated five/six-heterocyclic compounds and small molecules have been studied at M062X/aug-cc-PVTZ level.Our studies contain three parts as follows:the 1p…π interaction and hydrogen bond between the halogenated six-heterocyclic compounds,fluorinated pyridines and fluorinated diazines(pyridazine,pyrimidine and pyrazine)and water are studied as the first part.The calculated IE(interaction energy)values show that perfluorinated substitution on pyridine is necessary for the existence of 1p…π complex,agreement with the experimental result.While for the fluorinated binary nitrogen-heterocycles,the lp…πcomplexes 3FPa-Ⅱ-LP and 3FPm-Ⅱ-LP with IE values of-19.3 kJ mol-1 and-16.9 kJ mol-1,respectively,are competitive with their corresponding hydrogen bond ones 3FPa-Ⅱ-HB(-19.7 kJ mol-1)and 3FPm-Ⅱ-HB(-16.5 kJ mol-1),which suggests that different from the case of tetrafluorinated pyridine,3FPa-Ⅱ-LP and 3FPm-Ⅱ-LP have the possibility to be investigated by the spectroscopy experiment.In the second part,1p…π interaction and halogen bond between the fluorinated/chlorinated pyridine C5NF5-nCln(n=1-5)and halide anion Cl-、Br-and I-are explored.The calculated IE values manifest that the fluorine atoms binding the para carbon relative the nitrogen of pyridine can intensify the 1p…π interaction.For the Cl-,Br-and I-,the Cl-has the strongest binding ability in contrast to Br-and I-.In the third part,1p…π interaction and halogen bond between the perchlorinated five-heterocyclic compounds and halide anion Cl-、Br-and I-are explored.The five-heterocyclic compounds include tetrachlorinated furan,trichlorooxazole and trichloroisoxazole.The obtained IE values reveal that the occurrence of nitrogen favors the 1p…π interaction,and the 1p…π complexes are more stable than their corresponding halogen bond complexes.The trichlorooxazole is the strongest ligand for 1p…π complexes.Electrostatic potential and AIM analyses explained the microscopic nature of the weak interactions from molecular scope.