Protonation‐Dependent Luminescence of an Iridium(III) Bibenzimidazole Chromophore

Abstract

We present the synthesis and a detailed structural and photophysical investigation of the bis(phenylpyridine)iridium(III) complex of 4,4Ј,5,5Ј-tetramethyl-2,2Ј-bibenzimidazole [Ir(tmBBI)-H 2 ] and its homodinuclear complex [Ir(tmBBI)Ir]. Their structures were determined by single-crystal X-ray diffraction analysis and NMR spectroscopy, and detailed UV/ Vis and emission spectroscopy studies were performed. Ir(tmBBI)-H x shows strong protonation-state-dependent lu-

Functional Dimming of Pincer‐Shaped Bibenzimidazole‐Ruthenium(II) Complexes with Improved Anion‐Sensitive Luminescence

“…[30] This aspect has already been discussed in detail for the related ruthenium complexes, and the tendency of bibenzimidazole ligands to bind two Hbond acceptor atoms stems from the rigidity of their framework, in contrast to related diamine/diimine ligands. [19] This is most prominently reflected by the bending of the ligand towards the metal center and subsequent widening of the cisdiamine geometry in the respective solid-state structures.…”

Covalent Photosensitizer–Polyoxometalate‐Catalyst Dyads for Visible‐Light‐Driven Hydrogen Evolution

“…Time-resolved emission spectroscopy determinedt he excited-state lifetime of 3 to approximately 360 ns (AE 5%). As an on-covalentr eferences ystem, the structurally relatedI rp hotosensitizer [Ir(ppy) 2 (bpy)] + (Ir') [43,44] and the TRIS-functionalized Anderson POM 1 wereu sed. [42] As these studies suggest significant energetic/electronic coupling within 3,w ee xamined the performance of 3 as ah omogenous,v isible light-driven HER catalyst.…”

Interaction of an Iridium(III)–Bibenzimidazole Complex with Anions – Implications for Luminescent Sensing

“…[40] When A stepwise shift towards the blue region of the spectra can be observed upon deprotonation.…”

“…[40] Doubly protonated complex IrBBI-H 2 shows a structured emission band with two clear maxima and one slightly developed shoulder ( Figure 1). [40] Doubly protonated complex IrBBI-H 2 shows a structured emission band with two clear maxima and one slightly developed shoulder ( Figure 1).…”

“…[2,[19][20][21][29][30][31]38,39] The three different protonation states of these ligands (biimH x , x = 0, 1, 2) are controlled by several factors: (1) the acidity of the metalloreceptor, (2) the basicity of the distinct anions, and (3) the strength and steric demand of the hydrogen bonding, which should be related to the charge and interaction between the hydrogen-bond-donor and -acceptor groups. [40] In principle, this feature may provide an effective spectroscopic handle for the direct observation of the interaction of the complex with various anions. [2,[19][20][21]29] Investigations with various anions and ruthenium-bibenzimidazole-type complexes revealed that the more basic anions fluoride and acetate are able to deprotonate the BBI ligand, whereas Cl -, Br -, I -, NO 3 -, HSO 4 and H 2 PO 4 can only build initial hydrogen bonds between the two N-H groups of the BBI-H 2 and themselves (Scheme 1).…”