Excitation Energy Transfer Supported Amplified Charge-Transfer Emission in an Anthracenedicarboxylate- and Bipyridophenazine-Based Coordination Complex.

A highly luminescent tetrameric zinc(II) complex, {[Zn4(adc)3(bpz)6(HCOO)2]·2H2O} (1; adc = 9,10-anthracenedicarboxylate and bpz = bipyridophenazine), was synthesized by a solvothermal technique and characterized by single-crystal X-ray diffraction. The linear tetrameric units extend into three dimensions via π stacking of adc/bpz and bpz/bpz and multiple CH-π interactions. The compound shows strong red emission at 597 nm (λex = 480 nm), which is attributed to charge-transfer (CT) emission within an adc/bpz donor-acceptor pair. This is also supported by density functional theory computations. Interestingly, the CT emission is amplified by energy transfer from another adc linker that is not involved in the CT interaction.