inorganic chemistry

f¼0.01 atlirr¼313 nm. Even at higher concentrations ofIchar-
acteristic LF bands of Cu(II) cannot be detected in the spectrum
of the photolyzed solution.
The photolysis ofIis accompanied by the formation of a gas
that already in the beginning becomes visible as small bubbles.
This gas is not CO 2 but CO. The photolysis can be described by
the simple stoichiometric equation:

CO 2 þprophos!COþprophos monoxide ð 27 Þ

On the basis of our observations and further considerations we
suggest that the photolysis proceeds by the following molecular
mechanism. In analogy to other Cu(I) phenylphosphine
complexes ( 37 ) including (Pf 3 ) 2 CuI(NO 3 )( 35 ) the long-wave-
length absorption ofIis attributed to an IL (phosphine) transi-
tion. Accordingly, the irradiation ofIis associated with an IL
excitation. Partially, the deactivation leads to an IL lumines-
cence (lmax¼440 nm). The IL emissions of comparable complexes
( 37 ) such as (Pf 3 ) 2 CuI(NO 3 ) at lmax¼450 nm ( 35 ) or
[CuI(prophos) 2 ]þ atlmax¼430 nm appear in the same spectral
region. Another deactivation path terminates at a reactive
(CuI!CO 32
) MLCT state which with participation of a suitable
vibration leads to the dissociation of CO from the carbonate
bridge (Fig. 3).
According to this description, the release of CO should be
accompanied by the generation of a CuO 2 Cu moiety in the pri-
mary photochemical step. This fragment may contain CuI(O 22
)
CuIor its redox isomer CuII(O^2
) 2 CuII. Calculations have shown

A

IL

E

prophos

CuO 2 Cu + CO

MLCT (CuI

E

CO 32 - )

FIG. 3. Potential energy diagram for the ground state and the lowest
energy excited states of (prophos)CuI(CO 3 )CuI(prophos).

356 ARND VOGLER AND HORST KUNKELY