Two π-radical complexes containing bisazo-aromatic-centered radical anion (1⋅-) were synthesized through in-situ electron transfer from metal-to-ligand using [IrI] and 2-(2-Pyridylazo)azobenzene (1) in inert hydrocarbon solvent. These are characterized as diradical [IrIII(1⋅-)2]+ [2]+ and monoradical [IrIII(1⋅-)Cl2(PPh3)] 3. In contrast, a rare metal-mediated hydrolytic cleavage of the C(sp2)-N bond occurred in protic solvent resulting in quaternary radical complex [IrIII(1⋅-)(1')(PPh3)]+ (4)+. This provides an easy way to synthesize stable unsubstituted pyridine-2-diazotate (1'), an otherwise unstable organic template. Theoretical scrutiny has been performed at (U)B3LYP/6-31G(d,p)/LANL2DZ level to explore the origin of redox and optical properties in radical complexes. Magnetic study of [2]+ reveals that a weak antiferromagnetic (AF) spin-communication (J = -4.39 cm-1) exists between two radicals, leading to an open-shell singlet ground state. Broken symmetry density functional theory (BS-DFT) calculations were carried out to probe the nature of antiferromagnetic exchange interaction between the two radical centers in species [2]+. This method has been employed with different basis functionals (BP86, BLYP, OLYP, TPSS0, TPSSh, ωb97D and B3LYP) to comprehend the nature of the exchange in [2]+. The best result is obtained for pure functional OLYP with a J value -8.4 cm-1.

Correction for 'Iridium-mediated C-S bond activation and transformation: organoiridium(III) thioether, thiolato, sulfinato and thiyl radical compounds. Synthesis, mechanistic, spectral, electrochemical and theoretical aspects' by Ujjwal Das et al., Dalton Trans., 2015, 44, 8625-8639, DOI: 10.1039/C5DT00448A.

The mononuclear Zn(II) complexes of general formula [Zn(L)(2)] 1have been synthesized in good yields by reacting Zn(OAc)(2)center dot 2H(2)O with HL in 1:2 stoichiometric ratio in methanol. In this work, L represents deprotonated form of 2,5-Bis(4-bromophenylazo)-1H-pyrrole (HL1), 2-(4-Bromophenylazo)-5-(4-dimethylaminophenylazo)1H-pyrrole (HL2) and 2,5-Bis(4-chlorophenylazo)-1H-pyrrole (HL3), respectively. Coordination mode and geometry of the complexes are authenticated by single crystal X-ray study of the representative complex 1a. The ligands exhibit strong binding ability and ratio metric response to Zn2+ ions. The electronic structure and luminescent behavior of both ligands and the complexes were analyzed by DFT and Time-dependent DFT method. The formation of 1:2 (M:L) complexes and their corresponding association constants, K-assoc (1a:7.2 x 10(4)M(-1), 1b: 8.1 x 10(6) and 1c: 1.02 x 10(4)M(-1)) have been estimated with the help of the Benesi-Hildebrand method. The calculated K-assoc values unequivocally suggest that the current ligand frameworks incorporating typical nitrogenous donors are superior complexing agent. Addition of Zn2+ ions to the ligands in a mixed aqueous solution leads to a twofold change viz. a sharp variation of colour from orange to violet which is imperative for naked eye detection as well as a significant enhancement of the fluorescence intensity during coordination. Additionally, we explored the sensing property of the ligands depending on the nature of the substituent. The importance of the present fluorescent probes (HL) is that they incorporate both electron-excess (pyrrole and aromatic rings) and electron-deficient (azo) domains and thereby govern the ligand-centered fluorescence property in a more controlled way.

Coordination diversity of an aromatic diamine with Rh(iii) is presented together with the elucidation of the molecular and electronic structures, electron transfer, and electronic transitions.

Luminescent nickel(ii) complexes have been synthesized using redox-active azo-oximes. The superior π-acidity of the organic backbone is a key to the isolation of Ni(ii) anion radicals.

Non-trivial coordination mode of symmetrical NNN ligands with Rh(iii) leads to redox-active NNO-scaffolds via C(sp2)–H oxyfunctionalization at rt, opening an opportunity to juxtapose different redox-active domains.

The hydrogen bonded bis azo-oximato [IrCl2(L(NOH))(L(NO))] 2 and its deprotonated form (Et3NH)[IrCl2(L(NO))2] (Et3NH)(+)3(-) have been isolated in the crystalline state by a facile synthetic method. The azo-oxime frameworks in 3(-) have been conveniently transformed to the azo-imine by reduction with NaBH4 or ascorbic acid. Notably, the coordinated azo-imines accept an extra electron thereby furnishing the azo-imine radical anion complex 4. The underlying reductive transformation can be best described by proton-coupled electron transfer (PCET) process. Both the coordinated ligands (azo-oxime) in 3(-) are typically closed-shell monoanion (L(NO-)), but their reduced form (azo-imine) can behave as open-shell monoanion (L(NH•-)) owing to the presence of highly stabilized virtual orbitals. Remarkable enhancement of the π-acidity in azo-imine relative to the precursor azo-oxime has also been reflected from the electrochemical study. The irido complexes display rich optoelectronic properties, and the origin of the transitions has been scrutinized by the TD-DFT method. The molecular geometries of the complexes 2 and 3(-) reveal that the syn orientation of the azo-oximes frameworks is favored because of strong noncovalent H-bonding and π-π stacking interactions. In the course of the reduction of 3(-), the sterically encumbered disposition of the azo-oximes is converted to the relaxed anti form in the transformed azo-imines. Diffraction study reveals the electronic structure of 4 as [Ir(III)Cl2{(L(NH))2(•-)}]. The superior stabilization of the unpaired spin on the ligand array rather than metal has also been substantiated from EPR and DFT studies. Theoretical analysis reveals that the odd electron delocalizes primarily over both the azo-imine moieties ([IrCl2(L(NH•-))(L(NH))] ↔ ([IrCl2(L(NH))(L(NH•-))]) with no apparent contribution from metal, and this type of ligand-centered mixed valency (LCMV) can be best expressed as Robin-Day class III (fully delocalized) in nature.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Reactions of alkyl/aryl (2-pyridylimine)phenyl thioether (LSR) with RuCl2(PPh3)3 in ethanolic medium afford thioether complexes of type [Ru(L-SR)Cl(PPh3)(2)]PF6 (R = benzyl, phenyl). The ligands behave as tridentate neutral NpyNimineSthioether donor retaining the C-S bond and bind to the metal atom in meridional fashion. The complexes were characterized by spectroscopic (IR, UV-Vis, and NMR) techniques. Crystallographic analysis reveals the octahedral geometry around ruthenium(H) with N2SP2Cl coordination. Complexes display rich optoelectronic features including luminescence. The complexes are electro-active and show quasi-reversible response near 1.1 V vs SCE. Theoretical (DFT) analyses were performed to explore the electronic transition and electron transfer behaviour.

The 2-(phenylazo)azobenzene furnished novel palladacycles in excellent yield, which showed luminescence at rt and catalytic activity. The optoelectronic and electrochemical responses were substantiated with DFT and TDDFT.

The reaction between a potential flexidentate pyridyl-azo-oxime HL1 and Co(ClO4)2 yields novel homoleptic complexes of types [Co(III)(L(-I))3], 2 and [Co(III)(L(-I))2]ClO4, 3⁺ClO₄ in N6 and N4O2 coordination environments respectively. The FMOs of these complexes vary appreciably and are strongly modified by the coordination environment. This has striking influences on the spectral and redox properties of the metallo conjugates of ligand HL. The synthesized bis 2 and tris chelates 3⁺ possess well-defined optoelectronic and redox properties and these are scrutinized by the density functional theory (DFT) and time dependent density functional theory (TD-DFT) analyses. The visible excitations are primarily mixed singlet-manifold (1)ILCT and (1)LLCT transitions, with different amounts of ligand π-π* character while in the UV region, the excitations are essentially π-π* ILCT/LLCT transitions for the 3⁺ and ILCT/LLCT transitions along with the LMCT component for 2. The luminescent cobalt(III) species are rarely cited albeit these are found to be moderately blue emissive with slight quenching of the emission quantum yield (Φ) as compared to that of a free ligand. Computation reveals that the cobalt d orbital is involved in the triplet emissive excited states and this phenomenon is plausibly responsible for the quenching of the emission quantum yield in the complexes. Both types of complexes are electro-active in solution and the first reductive response, associated with the redox orbital comprising delocalized π orbital of a ligand, is shifted in the more positive potential (0.6 V) in 3⁺ relative to 2 and this observation is corroborated with the appreciable stabilization (~0.5 eV) of LUMO of 3⁺ (coordination mode A) as compared to that in 2 (coordination mode B). This provides us an opportunity to explore the cobalt-bound azo-oxime anion radical compound by reduction of the diamagnetic precursor 3⁺. The best description of the one-electron paramagnetic 3 can be ascertained as [Co(III){(L(-I))2}˙(-)] from the EPR and DFT studies where the unpaired spin is delocalized essentially over π* orbital comprising both the coordinated ligands (97%) with little participation of cobalt d(yz) (3%).