inorganic chemistry

and excimeric emissions derived from the stacking of the
platinum(II) 2,6-bis(1-tetradecylpyrazol-3-yl)pyridyl moieties in
the film.
In a different approach, Bruce and coworkers( 210 ) described
the preparation of liquid-crystalline derivatives of a N,C,N-Pt
(II) luminophore (Fig. 18). Interestingly, they found that emis-
sion in the liquid-crystal phase is characteristic of the monomeric
complex, while excimer-like emission normally characterizes
nonliquid-crystalline analogues. They showed that the emission
of pure films is responsive to both method of preparation and
tribological stimulation so that it is possible to switch in a
controllable manner between monomer- and excimer-like states.
Bruce et al.( 211 ) also investigated the liquid crystalline
and luminescent properties of two rod-like, orthoplatinated
complexes bearing ab-diketonate coligand (Fig. 19).
The parent ligands exhibit a rich, smectic polymorphism, but
when modified with a fused cyclopentene ring, nematic phases
dominate. Reaction of the ligands with tetrachloroplatinate(II)
leads to poorly soluble, dimeric complexes that can be cleaved
using dimethylsulfoxide; the resulting monomeric complexes
are then readily converted to theb-diketonate complexes. All of
the complexes are mesomorphic, and theb-diketonate complexes

2000

2000

l l

3000

4000

5000

1500

1000

1000 500

500 550 600 650

l (nm)

500 550 600 650 700 750 800

l (nm)

700 750 800

0 0

OCnH 2 n+1

OCnH 2 n+1

OCnH 2 n+1

OCnH 2 n+1

CnH 2 n+1O

CnH 2 n+1O

N

N

PtCl

FIG. 18. Selected structure of Pt(II) complexes. Forn¼6, at room
temperature, top: real samples of pure films sandwiched between glass
slides; bottom: emission spectra (excitation at 420 nm). Left: fast cooled
from the LC phase after the texture is fully developed. Right: fast
cooled direct from the isotropic phase. Reproduced with the permission
of Wiley-VCH ( 210 ).

80 CRISTIAN A. STRASSERTet al.