Marigold Flower-Like Assemblies of Phosphorescent Iridium-Silver Coordination Polymers

Racemic and enantiopure phosphorescent iridium(III)-silver(I) coordination polymers are reported. The polymers rac-, Λ-, and Δ-IrAg were formed, respectively, by the assembly of the chiral iridium metalloligands rac-, Λ-, and Δ-[Ir(mesppy)₂ (qpy)]PF₆ (rac-, Λ- and Δ-Ir) where mesppy is 2-phenyl-4-mesitylpyridinato and qpy is 4,4':2',2'':4'',4'''-quaterpyridine, and Ag⁺ ions through N_py -Ag linear coordination. The polymers have been characterized in MeNO₂ solution by ¹ H and ¹ H DOSY NMR and CD spectroscopies and in the solid-state by scanning electron microscopy (SEM). The crystal structures of the racemic polymer rac-IrAg has been obtained by X-ray diffraction. The polymers rac-, Λ-, and Δ-IrAg exhibited orange/red emission in solution, in films and as crystals, with intensities comparable to those of the corresponding iridium metalloligands rac-, Λ-, and Δ-Ir. The morphology of the enantiopure polymers in the solid-state resembles marigold flower-like nano-porous assemblies while the racemic polymer possesses an irregular morphology formation.

Tunable high-performance microwave absorption for manganese dioxides by one-step Co doping modification

The frequencies of microwave absorption can be affected by the permanent electric dipole moment which could be adjusted by modifying the crystal symmetry of the microwave absorbing materials. Herein, we corroborate this strategy experimentally and computationally to the microwave absorption of manganese dioxides. Nanosized Co-doped cryptomelane (Co-Cryp) was successfully synthesized by a one-step reaction. The introduction of Co(III) induced a change of crystal symmetry from tetragonal to monlclinic, which could lead to an increase of its permanent electric dipole moment. As a result, the frequencies of maximum microwave absorption were regulated in the range of 7.4 to 13.9 GHz with a broadened bandwidths. The results suggested that microwave absorption of manganese dioxides can be tailored with Co doping to expand their potential uses for abatement of various microwave pollutions.