Synthesis, Structure and Luminescent Properties of Rare Earth Coordination Polymers Constructed from Paddle-Wheel Building Blocks

A series of three-dimensional (3D) novel coordination polymers M(bpdc)1.5(H2O)·0.5DMF (M = Tb (1), Ho (2), Er
(3), or Y (4)) have been synthesized by reaction of the rare earth ions (M3+) with 4,4‘-biphenyldicarboxylic acid
(H2bpdc) in a mixed solution of DMF and C2H5OH. They possess the same 3D architectures and crystallize in
monoclinic space group C2/c. Two seven-coordinated metal centers and four dimonodentate bpdc groups construct
a paddle-wheel building block. These building blocks connect with two carboxyl groups to lead to a one-dimensional
inorganic chain, ---M−O−C−O−M---, along the [001] direction. The inorganic chains are linked with two biphenyl
groups to form 25.15 Å × 17.09 Å rhombic channels along the c axis without interpenetration. These complexes
exhibit strong fluorescence in the visible region, and complex 3 shows Er3+ characteristic emission in the range of
1450−1650 nm at room temperature. These complexes could be anticipated as potential fluorescent probes and
an IR-emitter, respectively.