CH(X-2 Pi, a(4)Sigma(-))... OH2 and CH2 ((X)over-tilde(3)B(1),(a)over-tilde(1)A(1)... OH2 interactions. A first principles investigation

摘要

We have investigated the interaction of the methylidene, CH(X(2)Pi, a(4)Sigma(-)) and methylene, CH2((X) over tilde B-3(1),(a) over tilde (1)A(1)) with H2O, employing the (P)MPn (n = 2, 4) techniques in conjunction with the sequence of correlation consistent basis sets aug-cc-pVxZ, x = 2, 3, and 4. For the CH...CH2 system, we have located four minima (m) and three transition states (ts) and for the CH2...OH2, five minima and four transition states. All our results have been corrected for zero-point energy (ZPE) and basis set superposition errors (BSSE), while for the most important m_ structures, we report complete basis set (CBS) interaction limits. We also report fully optimized geometries, harmonic frequencies, dipole moments, Mulliken charges, and potential energy curves. The highest CH(X(2)Pi)...OH2 (m1_(2)Pi) and CH2((a) over tildeA(1))...OH2 (m1_(1)A(1)) interactions are the result of electron transfer from the oxygen atom to the empty p(pi) orbitals of CH(X(2)Pi) and CH2((a) over tilde (1)A(1)), respectively (yfide-like structures). At the (P)MP4/AQZ//MP2/ATZ level, including ZPE, BSSE, and CBS extrapolation, we obtain Delta E-0(BSSE)+CBS = -9.36 kcal/mol at r(C...O) = 1.752 angstrom, and -9.73 kcal/mol at r(C...O) = 1.741 angstrom for the m1_(2)Pi and m1_(1)A(1), respectively. (c) 2005 Wiley Periodicals, Inc.