Subject: HOMO-LUMO gap in Pt(II)

From: Jirka Kozelka <[email-masked]>
Date: Thu, 22 Apr 1999 12:01:25 -0700

Dear CCL-members,

I have carried out a number of SCF calculations on Pt(II) complexes with
chloride, amine, and phosphine ligands, using Gaussian 94 and 98, with
different basis sets, and find consistently HOMO-LUMO gaps of 0.3-0.4
Hartrees, i.e., 65000-90000 cm-1. This is roughly 3 times the excitation
energies of spin-allowed d-d bands seen in
solutions of these species. The difference seems too big to me to be
explained by electron relaxation. I would very much appreciate comments
and/or explications on/of this apparent discrepancy.
We have seen that the bond lengths and dipole moment coming from HF
calculations are quite wrong for these compounds, and one has to apply 
correlated methods to get these quantities right. But can it be that the
difference in energies of the HF HOMO/LUMO one-electron orbitals is so
far from the excitation energy?

I shall summarize the answers.

Thanks,

Jirka Kozelka

-- 
Jirka Kozelka
Universite Rene Descartes
URA CNRS 400
45 rue des Saints-Peres
75270 Paris 06
FRANCE
Tel. +331 42 86 21 75
Fax  +331 42 86 83 87
E-mail: [email-masked]