We report on the photophysical studies of two cationic near-UV emitters based on bis-pincer Ir(III) carbene complexes: [Ir(nBu)(C(NHC)(Me)CC(NHC))2]X, where Ir(nBu)(C(NHC)(Me)CC(NHC)) is (4,6-dimethyl-1,3-phenylene-κC(2))bis(1-butylimidazol-2-ylidene) and X = I(-) or PF6(-)). The compounds are highly emitting in deaerated CH3CN solution with emission maxima at 384 and 406 nm, and photoluminescence quantum yields of 0.41 and 0.38, for [Ir(nBu)(C(NHC)(Me)CC(NHC))2]I and Ir(nBu)(C(NHC)(Me)CC(NHC))2]PF6, respectively. In order to gain deeper understandings into their structural and electronic features, as well as to ascertain the nature of the excited states involved into the electronic absorption processes, density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations have been performed on the ground and excited states of the closely related complex [Ir(Me)(C(NHC)(Me)CC(NHC))2](+). In the solid state, an emission at low energy is observed (λ(max) = 500 nm) for both complexes. However, the intensity of the emission at high energy versus the intensity of the new emission at low energy is dependent on the nature of counterions. The origin of this emission is not completely clear, but the experimental data point to the formation of trapping sites induced by aggregation processes involving the interaction between the cationic emitter and the counterion.

We report on a series of blue and deep-blue emitting zwitterionic iridium(III) complexes, consisting formally of a cationic Ir centre and a N,N 0 -heteroaromatic (N^N) ligand bearing negatively charged side groups, i.e. sulfonate and borate. The synthesis, photophysical and electrochemical properties of this series are described in detail together with their X-ray crystal structure determination. The reported complexes exhibit intense blue (l max at 450 nm) and deep blue (l max at 435 nm) emission in deaerated solution, similar to the related cationic complexes. The strategy employed, namely the internal salt formation, allows high solubility in many organic solvents as well as for some of the complexes a low sublimation temperature. For this reason, one of the complexes was further tested as an emitter in phosphorescent organic light emitting diodes (PhOLEDs). Despite the zwitterionic nature of the triplet emitter employed, the devices were fabricated by means of sublimation process. The devices showed a peak external quantum efficiency (EQE) as high as 11.0% and Commission Internationale d'Énclairage (CIE) coordinates x ¼ 0.21 and y ¼ 0.33.

Electrochemical biosensors have attracted a tremendous attention for many researchers recently due to its facile synthesis process, tunability easiness by tailoring the material properties or composition, and wide range of biological analyte types detection. To obtain an excellent electrochemical biosensor performance, a material that facilitates fast electron transfer, large surface area, excellent electrocatalytic activity, and abundant available sites for bioconjugation is immensely needed. Metal-organic frameworks in the two-dimensional form (2D MOFs) provide all of the criteria needed as the sensing material for electrochemical biosensors application. However, the design and preparation of 2D MOFs, which have high stability and sensitivity as well as good selectivity for biological analyte detection, is still quite challenging. This review provides the recent studies and development of 2D MOFs as electrochemical biosensor. A detailed discussion about 2D MOFs structures, their synthesis strategy and control, 2D MOFs materials in electrochemical biosensor application, and the future challenges is thoroughly explained in this review. Hopefully, this review will also provide a new inspiration to advance future studies of 2D MOFs materials development as electrochemical biosensor.