inorganic chemistry

(Sw¼33.6 and 38.1 for11band11c, respectively), this clearly
shows that interligand p–pinteractions between the aromatic
diimine ligand and the aryl groups in the phosphine ligands have
a profound influence on the photophysical properties of the com-
plex. Close contacts between the two aromatic moieties in the solid
state were observed by X-ray crystallography and in solution by
nuclear magnetic resonance (NMR) and infrared spectroscopies.
The interligand aromatic interactions decrease the nonradiative
decay rate constant from the^3 MLCT excited state of the complex,
prolong the excitation lifetime, and strengthen the oxidation
power of the complex.

300

(a)

absorption

maximum

emission

maximum

non radiative

decay

rate constant

bathochromic shift

p–p interaction

iPrO

iPrO

iPrO

N

N

iPrO

OiPr

OiPr

CO

Cl

Cl

Cl

Cl

Cl

Cl

CO

N CO

N

P

P

Re CO Re

P

P

without

11c 11b

p–p interaction

with

hypsochromic shift

decrease

(b)

350 400

wavelength (nm)

abs.

emission intensity/a.u.

wavelength (nm)

450 500 450 500 550 600 650 700 750

FIG. 6. The effects of the interligandp–pinteraction to the funda-
mental properties of rhenium(I) complexes. The absorption (a) and
emission (b) spectra of rhenium(I) complexes with (11b, solid line)
and without (11c, dotted line)p–pinteraction.

RHENIUM(I) DIIMINE COMPLEXES 145