3 research outputs found
Ultrafast Photochemistry of Copper(II) Monochlorocomplexes in Methanol and Acetonitrile by Broadband Deep-UV-to-Near-IR Femtosecond Transient Absorption Spectroscopy
Photochemistry
of copper(II) monochlorocomplexes in methanol and
acetonitrile solutions is studied by UV-pump/broadband deep-UV-to-near-IR
probe femtosecond transient absorption spectroscopy. Upon 255 and
266 nm excitation, the complexes in acetonitrile and methanol, respectively,
are promoted to the excited ligand-to-metal charge transfer (LMCT)
state, which has a short (sub-250 fs) lifetime. From the LMCT state,
the complexes decay via internal conversion to lower-lying ligand
field (LF) d–d excited states or the vibrationally hot ground
electronic state. A minor fraction of the excited complexes relaxes
to the LF electronic excited states, which are relatively long-lived
with lifetimes >1 ns. Also, in methanol solutions, about 3% of
the
LMCT-excited copper(II) monochlorocomplexes dissociate forming copper(I)
solvatocomplexes and chlorine atoms, which then further react forming
long-lived photoproducts. In acetonitrile, about 50% of the LMCT-excited
copper(II) monochlorocomplexes dissociate forming radical and ionic
products in a ratio of 3:2. Another minor process observed following
excitation only in methanol solutions is the re-equilibration between
several forms of the copper(II) ground-state complexes present in
solutions. This re-equilibration occurs on a time scale from sub-nanoseconds
to nanoseconds