Pulsed-field ionization zero electron kinetic energy spectroscopy and theoretical calculations of copper complexes: Cu–X(CH[sub 3])[sub 3] (X=N,P,As).

The copper complexes were produced in pulsed laser vaporization molecular beams and investigated by pulsed-field ionization zero electron kinetic energy (ZEKE) spectroscopy and second-order Møller–Plesset (MP2) perturbation and hybrid B3LYP density functional theory calculations. The ground electronic states of Cu–X(CH[sub 3])[sub 3] and Cu[sup +]–X(CH[sub 3])[sub 3] (X=N,P,As) are [sup 2]A[sub 1] and [sup 1]A[sub 1], respectively, both with C[sub 3v] symmetry. From the ZEKE spectra, the adiabatic ionization potentials of the neutral molecules are determined to be 44 730, 41 508, and 42 324 cm-1, and the Cu[sup +]/Cu–X stretching frequencies are 268/199, 214/187, and 188/155 cm-1 for X=N, P, and As, respectively. The degenerate Cu[sup +]/Cu–P–C and Cu[sup +]/Cu–As–C bending frequencies are measured to be 146/83 and 118/52 cm-1, while the Cu[sup +]/Cu–N–C mode was not observed. In addition, the CH[sub 3] wag, X–C stretching, and XC[sub 3] umbrella modes are also measured for the phosphine and arsine complexes. From the MP2 theory, the dissociation energies of the Cu[sup +] and Cu complexes are estimated to be 59/12, 70/15, and 65/11 kcal mol-1 down the X group. Both MP2 and B3LYP predictions of ionic vibrational frequencies compare well with the spectroscopic values, but the B3LYP calculations of neutral low frequency modes are less satisfactory. On the other hand, the B3LYP calculations yield better ionization potentials than the MP2 methods for these molecules. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]