inorganic chemistry

“molecular polygons”because various kinds of molecules could be
introduced into these complexes as the diimine ligand and the
monodentate ligand X (Fig. 14a ( 44 ),b( 45 ),c( 45 ),d( 46 )). Many
of these molecular polygons emit in solution even at room
temperature.
Recently, a series of linear-shaped rhenium multinuclear
complexes were synthesized by applying the photochemical
ligand substitution reaction of the rhenium(I) diimine complexes
with a phosphorus ligand to the rhenium(I) binuclear complexes
bridged with a bidentate phosphorous ligand. First, two CO lig-
ands in the trans-position to the phosphorous ligands were pho-
tochemically substituted sequentially with CH 3 CN, which can
be easily substituted by thermal activation (Scheme 5) ( 47 ). This
product can be polymerized by the reaction with the appropriate
amount of a bidentate ligand such as bidentate phosphorous lig-
ands and 4,4^0 -bipyridine ( 48 – 50 ). This produces linear-shaped
rhenium(I) multinuclear complexes with 2–20 nuclei, which were
successfully isolated by size-exclusion chromatography (Fig. 15).
All the linear-shaped multinuclear complexes emit in solution
at room temperature. Although UV/Vis light can be absorbed
by all the Re(I) units, most of the emission comes from the inte-
rior Re(I) biscarbonyl unit(s) because excitation energy absorbed

N

NN NN

C 6 H 13 C 6 H 13 C 6 H 13 C 6 H 13 C 6 H 13 C 6 H 13

xy

n m

(b)

2 n

Ar Ar

N

Re

(CO) 3 CI

Ar =

(a)

(d)

(c)

0.01 0.99

O O

O

N

N

CO

CO

CO

+

N

Re

O

NNReCI

OCCOCO

N

N COCO

CO

+

N N+ N+

Re

N

N

CO

CO

CO

+

200

200

N NN N

Re

FIG. 13. Polymer molecules containing rhenium(I) tricarbonyl
complexes as pendant molecules.

RHENIUM(I) DIIMINE COMPLEXES 161