摘要
Geometries and binding energies were predicted at the B3LYP/6-311＋G＊ level for the guanine-BX3 （X = F, Cl） systems and four isomers with no imaginary frequencies have been obtained for both guanine-BF3 and guanine-BCl3, respectively. Single energy calculations using much larger basis sets （6-311＋G（2df, p） and aug-cc-pVDZ were carded out as well. It was found that the most stable isomer of guanine-BF3 is BF3 connected to N3 of guanine with the stabilization energy of-19.93 kcal/mol （BSSE corrected）, while that of guanine-BC13 is BC13 connected to O10 of guanine having stabilization energy of -15.02 kcal/mol at the same level. The analyses for the combining interaction between BX3 and guanine with the atom-in-molecules theory （AIM） and natural bond orbital （NBO） methods have been performed. The results indicated that all the isomers are formed with σ-p type interactions between guanine and BX3, in which pyridine-type nitrogen or carbonyl oxygen or nitrogen atom of amino group offers its lone pair electrons to the empty p orbital of boron atom and the concomitance of charge transfer from guanine to BX3 has occurred. Still, one or two hydrogen bonds exist in some isomers of guanine-BX3 system and contribute to the stability of complex systems. Frequency analysis suggested that the stretching vibration of BX3 undergoes a red shift in complexes. Guanine-BF3 complex is more stable than guanine-BC13 although the B-Y （Y=N, O） bond distance in the latter is shorter.
Geometries and binding energies were predicted at the B3LYP/6-311＋G＊ level for the guanine-BX3 （X = F, Cl） systems and four isomers with no imaginary frequencies have been obtained for both guanine-BF3 and guanine-BCl3, respectively. Single energy calculations using much larger basis sets （6-311＋G（2df, p） and aug-cc-pVDZ were carded out as well. It was found that the most stable isomer of guanine-BF3 is BF3 connected to N3 of guanine with the stabilization energy of-19.93 kcal/mol （BSSE corrected）, while that of guanine-BC13 is BC13 connected to O10 of guanine having stabilization energy of -15.02 kcal/mol at the same level. The analyses for the combining interaction between BX3 and guanine with the atom-in-molecules theory （AIM） and natural bond orbital （NBO） methods have been performed. The results indicated that all the isomers are formed with σ-p type interactions between guanine and BX3, in which pyridine-type nitrogen or carbonyl oxygen or nitrogen atom of amino group offers its lone pair electrons to the empty p orbital of boron atom and the concomitance of charge transfer from guanine to BX3 has occurred. Still, one or two hydrogen bonds exist in some isomers of guanine-BX3 system and contribute to the stability of complex systems. Frequency analysis suggested that the stretching vibration of BX3 undergoes a red shift in complexes. Guanine-BF3 complex is more stable than guanine-BC13 although the B-Y （Y=N, O） bond distance in the latter is shorter.
基金
the National Natural Science Foundation of China (No. 20171031 and 20471033)
