Iridium(III) complexes based on 5-nitro-2-(2′,4′-difluorophenyl)pyridyl: Syntheses,structures and photoluminescence properties

A series of cyclometalated Ir(III) complexes [Ir(dFNppy)₂(PPh₃)L] (PPh₃ = triphenylphosphine, L = Cl⁻, 1; NCS⁻, 2; NCO⁻, 3; N₃⁻, 4) in which 5-nitro-2-(2′,4′-difluorophenyl)pyridyl (dFNppy) is used as the main ligand are synthesized and characterized. The crystal structures of 3 and 4 are determined by X-ray diffraction analyses. Photoluminescence spectra of 1–4 in CH₂Cl₂ solutions at room temperature show the maximum emission wavelengths (λ_max) in the range from 586 to 627 nm, corresponding to red-orange luminescence. HOMO–LUMO energy levels of 1–4 are estimated by cyclic voltammetry measurements. Compared with corresponding 2-phenylpyridyl (ppy)-containing Ir(III) complexes having same ancillary ligands, 1–4 have obviously smaller HOMO–LUMO energy gaps (E_g). Simultaneously, 1–4 show relatively bigger E_g compared with 2-phenyl-5-nitropyridyl (5-NO₂-ppy)-containing Ir(III) complexes possessing same ancillary ligands. Methods of E_g adjustment are also discussed.     

Photo- and electroluminescence from deep-red- and near-infrared-phosphorescent tris-cyclometalated iridium(III) complexes bearing largely π-extended ligands

Deep-red- and near-infrared-phosphorescent tris-cyclometalated iridium(III) complexes bearing largely π-extended cyclometalated (C^N) ligands were newly synthesized, and their photo- and electroluminescence properties were investigated. When 2-(benzo[b]furan-2-yl)quinoline and 2-(benzo[b]thiophen-2-yl)quinoline were employed as C^N ligands, deep-red photoluminescence was obtained (Ir-1a and Ir-1b; λ_PL in CH₂Cl₂, 647 and 652 nm, respectively). In the case of the isoquinoline analogues of Ir-1a and Ir-1b, emission maxima were further red-shifted, ranging from deep-red to near-infrared regions (Ir-2a and Ir-2b; λ_PL in CH₂Cl₂, 696 and 690 nm, respectively). Especially, Ir-2b showed an excellent photoluminescence quantum yield (Φ_PL = 0.15), and a polymer light-emitting diode doped with Ir-2b exhibited deep-red–near-infrared electroluminescence with a high external quantum efficiency (λ_EL = 694 nm, η_{ext max} = 1.41%).     

Synthesis,structural characterization,opto-electrical properties of Ir(III) complexes with imidazolium-based carbene ligands

A series of Ir(III) complexes with N–heterocyclic carbenes (NHC) ligands (1–3) were synthesized and characterized. The opto-electrical properties of these complexes were investigated spectroscopically, electrochemically and theoretically. All complexes exhibit ligand-based ¹π,π* transitions in the UV region, ¹MLCT absorption in the UV region, and weak low energy ³π, π* transition in visible region. These complexes all exhibit blue phosphorescence at both room temperature and 77 K, which is dominated by ³π,π* character. DFT calculation results indicate their lowest unoccupied molecular orbitals (LUMO) from − 0.47 to − 0.33 eV and the highest occupied molecular orbitals (HOMO) from − 4.97 to − 5.33 eV. The opto-electrical properties can be influenced drastically by NHC ligands, which would be useful for rational design of optical functional materials.     

Binuclear rhodium(III) and iridium(III) monoselenocarboxylates: Synthesis,spectroscopy and structure of an ortho-metallated iridium complex featuring an IrCCC(μ-Se) chelate ring

Monoselenocarboxylate–bridged binuclear complexes of Rh^III and Ir^III, [(Cp1MCl)₂(μ-SeCOAr)₂] (1) (M = Rh or Ir; Cp1 = pentamethylcyclopentadienyl; Ar = Ph, C₆H₄Me–4), have been isolated either by the reaction between [Cp1₂M₂(μ-Cl)₂Cl₂] with KSeCOAr in acetonitrile or by treatment of [Cp1MCl(solvent)₂][PF₆] with KSeCOAr in acetone. The novel binuclear complexes, [Cp1IrCl(μ-SeCOAr)(κ²-SeCOC₆H₃R–)IrCp1] (2) (R = H or Me-4) with ortho-metallation at one of the iridium centres have been isolated following the use of excess AgPF₆. The single crystal structure of [Cp1IrCl(μ-SeCOC₆H₅)(κ²-SeCOC₆H₄–)IrCp1] (2a) exhibits two phenylcarboselenolate moieties situated in syn fashion with respect to the “Ir₂Se₂” plane, one of which leans towards the metal centre in order to undergo ortho-metallation after iridium–chlorine bond dissociation.     

Synthesis,characterization and photoluminescence properties of copper(II)–azido/thiocyanato complexes with thiazolylazo dye and1,2-bis(diphenylphosphino)ethane

A series of copper(II) complexes of the formula [Cu(L)(dppe)(N₃)₂] (1a–3a) and [Cu(L)(dppe)(NCS)₂] (1b–3b) (where L = 4-(2′-thiazolylazo)chlorobenzene (L₁); 4-(2′-thiazolylazo)bromobenzene (L₂) and 4-(2′-thiazolylazo)iodobenzene (L₃); dppe = cis-1,2-bis(diphenylphosphino)ethane) has been prepared and characterized on the basis of their elemental analysis, molar conductance, magnetic moment, IR, UV–vis and ¹H NMR spectral studies. The electrochemical behaviour of the complexes showed that the redox responses of copper(II) complexes shifted to more negative potential in order of decrease in electron withdrawing nature of the substituent on the azo ligands. All the complexes exhibit intraligand (π→π*) fluorescence in blue-green region with high quantum yield in DMF solution.     

Sandwich type organic-inorganic hybrid of 3d–4f heterometallic containing germanotungstates [{Cu2(1,10-phen)2(μ-CH3COO)2}Ln(α-GeW11O39)2]11 −: Syntheses,crystal structures,magnetic and photoluminescence properties

Alkali salts of organic-inorganic hybrid 3d-4f heterometallic containing derivatives of sandwich type germanotungstates: [{Cu₂(1,10-phen)₂(μ-CH₃COO)₂}Ln(α-GeW₁₁O₃₉)₂]^11 − [Ln = Pr^III (1a), Nd^III (2a), Sm^III (3a), Eu^III (4a), Gd^III (5a); 1,10-phen = 1.10-phenanthroline] have been prepared in the aqueous potassium acetate buffer (pH 4.7) solution. All these compounds were synthesized following by one pot reaction procedure under mild reaction conditions. All compounds were isolated as mixed alkali sodium/potassium salts from the solution and used for further structural characterization by single crystal XRD, powder-XRD, FT-IR, liquid UV/vis, solid state photoluminescence spectroscopy and thermo-gravimetric analysis. FT-IR spectra and powder-XRD pattern suggest that all compounds (1a–5a) are isomorphous. Further single crystal XRD analysis shows that all these compounds exhibit sandwich-type [Ln(α-GeW₁₁O₃₉)₂]^13 − structural feature in the polyoxoanions as the fundamental building block units, and the copper complexes coordinated with 1,10-phen and acetate ligands are coordinated to the terminal oxygen of the polyanion. The compounds 1a, 3a and 4a show good photoluminescence properties at room temperature. The compound 5a shows weak ferromagnetic behavior.     

PNBE-supported metallopolymer-type hybrid materials through grafting of Ln3-benzimidazole-arrayed (Ln = Nd,Yb or Er) complex monomers with efficient NIR luminescence

Through the ring-opening metathesis polymerization (ROMP) of norbornene (NBE) with each of the obtained allyl-containing complex monomers {[Ln₃(L)₄Cl₄(MeOH)₂]·Cl} (Ln = La, 1; Nd, 2; Yb, 3; Er, 4 or Gd, 5; HL = 4-allyl-2-(1H-benzo[d]imidazol-2-yl)-6-methoxyphenol), a series of metallopolymers Poly({[Ln₃(L)₄Cl₄(MeOH)₂]·Cl}-co-NBE) were obtained, respectively. Especially for Poly(NBE-co-2) and Poly(NBE-co-3), covalently-bonded grafting endows significantly improved physical properties including efficient NIR luminescence (Φ_Nd^L = 0.58% and Φ_Yb^L = 0.88%) in solid state.     

Synthesis,characterization and DNA interaction of copper (II) complexes with Schiff base ligands derived from 2-pyridinecarboxaldehyde and polyamines

A series of copper (II) complexes a–d with Schiff bases ligands derived from the condensation reactions between 2-pyridinecarboxaldehyde and different polyamines (ethylenediamine, diethylenetriamine, triethylenetetramine and tetraethylenepentamine) were synthesized and characterized by elemental analysis, FT-IR spectroscopy, HRMS, molar conductance and molecular modeling studies. The interactions of the copper complexes a–d with DNA were investigated by the UV spectra, viscosity measurements and gel electrophoresis under physiological conditions. The experimental results indicated that four complexes could bind to DNA via an intercalative mode and showed a different DNA cleavage activity with the sequence: d > c > a > b.     

A highly selective turn-on sensor for Hg2 + based on a phosphorescent iridium (III) complex

A highly selective phosphorescent chemosensor for Hg^2 + based on the iridium (III) complex Ir(DTBT)₂(acac) (DTBT = 2-(5-(1,2 dihydroacenaphthylen-5-yl)thiophen-2-yl)benzothiazole, acac = acetylacetone) was synthesized and characterized. Ir(DTBT)₂(acac) exhibited relatively weak fluorescenceat at about 700 nm. Ir(DTBT)₂(acac) displayed a dramatic color change from near-infrared to yellow-green with the addition of Hg^2 +. More significantly, the chemosensor performed “turn-on” phosphorescent responses toward Hg^2 +.     

Luminescent mononuclear Pt(II) chloride complexes with C-linked 2,2′-bipyridyl tetrazole terdentate chelating ligands

Two new luminescent mononuclear Pt(II) chloride complexes possessing C-linked 2,2′-bipyridyl tetrazole terdentate chelating ligands, namely, Pt(tbpy)Cl (1) and Pt(tmbpy)Cl (2) (tbpyH = 6-(1H-tetrazol-5-yl)-2,2′-bipyridine; tmbpyH = 6-(1H-tetrazol-5-yl)-4,4′-dimethyl-2,2′-bipyridine), have been synthesized and characterized. Complex 2 adopts a distorted square-planar geometry with a mono-anionic terdentate chelate tmbpy, and it presents a zigzag head-to-tail stacking array along the a axis with alternating Pt⋯Pt separations of 3.415 and 5.469 Å. For 2, a moderately intensive broad absorption band appears at 350–425 nm in dilute DMF solution, most likely assigned as the metal-to-ligand charge transfer ¹MLCT (Pt(5d) → tmbpy) transition, mixed with some halide-to-ligand charge transfer ¹XLCT (Cl → tmbpy) and intraligand (IL) ¹ππ* transitions inside tmbpy. It is demonstrated that the solubilities and luminescence properties of 1 and 2 are markedly influenced by the substituents in the 4 and 4′-positions of the 2,2′-bipyridyl ring. The solid-state emissions of 1 and 2 are perhaps best attributable to the ³MMLCT/³XLCT/³IL states, as supported by TD-DFT calculation of 2.     

Ligand concentration and reaction time controlled successive substitution of chloro and η6-benzene of di-μ-chlorobis{η6-benzene)dichlororuthenium(II)} with selenated Schiff base: Formation of half sandwich Ru(II) complex highly active catalyst for oxidation of alcohols

Schiff base (L) synthesized by reacting 2-methylthiobenzeldehyde with 2-(phenylseleno)ethylamine on reaction with di-μ-chlorobis{η⁶-benzene)dichloro-ruthenium(II)}(a) forms two type of species: (i) [Ru(L)₂][PF₆]₂ (1) [L:a = 4:1 and reaction time ～8 h] and (ii) [Ru(η⁶-C₆H₆)(L)][PF₆]₂ (2) [L:a = 2:1 and reaction time ～1 h]. This is first example in which chloro as well benzene ring both are successively substituted by controlling metal:ligand ratio and duration of reaction. The geometry around Ru in complex 1 is distorted octahedral. The 2 has a pseudo-octahedral half sandwich “piano-stool” disposition of ligands around Ru. The Ru–Se distances are 2.4683(10)–2.5082(7) ?. The proton and carbon-13 NMR spectra of L and its both complexes 1 and 2 authenticate them. The 2 shows high catalytic activity for oxidation of primary and secondary alcohols both (TON upto 9.6 × 10⁴; TOF upto 4.80 × 10⁴ h^?1).     

Synthesis and ion responsiveness of optically active polyacetylenes containing salicylidene Schiff-base moieties

Acetylenic monomers containing salicylidene Schiff-base groups (1a and 1b) as well as Schiff-base and hydroxy groups (1c) were synthesized and polymerized with [(nbd)RhCl]₂/Et₃N catalyst to afford the corresponding polymers 2a–c with high molecular weights (M_n = 2.6–7.2 × 10⁵) in high yields (75–97%). Polarimetric, circular dichroism (CD), and UV–vis spectroscopic analyses indicated that the polymers formed helical structures with a predominantly one-handed screw sense. The addition of metal ions to salicylidene Schiff-base-containing polymers 2a and 2b produced insoluble polymer/metal complexes through ionic cross-linking as a result of salicylaldimine–metal ion complexation. Polymers 2b and 2c underwent a helix–coil transition upon the addition of HSO₄⁻, whereas these polymers did not exhibit responsiveness to other anions, such as F⁻, Cl⁻, and Br⁻.     

Hydrothermal syntheses and characterization of a series of mixed-ligand luminescent CdII frameworks with novel 2-(3-(pyridin-2-yl)-1H-pyrazol-1-yl) acetate ligand and benzenedicarboxylate isomers

Under similar hydrothermal synthetic conditions using a novel flexible ligand 2-(3-(pyridin-2-yl)-1H-pyrazol-1-yl)acetonitrile (PPAN), benzenedicarboxylate isomers (H₂pa = phthalate, H₂ip = isophthalate, and H₂tp = terephthalate) and Cadmium(II) acetate, three novel mixed-ligand Cd(II) coordination polymers {[Cd₂(PPAA)₂(μ-pa)(H₂O)]·2H₂O}_n (1), {[Cd₄(PPAA)₄ (μ₄-ip)₂]·2H₂O}_n (2) and {[Cd₂(PPAA)₂(μ-tp)]·2H₂O}_n (3) (PPAA⁻ = 2-(3-(pyridin-2-yl)-1H-pyrazol-1-yl) acetate) have been isolated, in 1–3 PPAN, and are also hydrolyzed into a novel PPAA⁻ ligand. Complex 1 is a 1D coordination polymer in which the tetra-nuclear [Cd₄(PPAA)₄]^4 + structural units are extended by tri-dentate μ-pa^2 − ligands. Complex 2 contains binuclear [Cd₂(PPAA)₂]^4 + structural units, which are extended by four tetra-dentate μ₄-ip^2 − ligands to link eight neighboring binuclear [Cd₂(PPAA)₂]^4 + units ultimately forming a 2D layered framework, while complex 3 contains 1D double chain containing [Cd(PPAA)]_n cation structural units, which are further extended by tetradentate μ-tp^2 − ligands to form a new 2D layered framework. All the complexes have been investigated by elemental analysis, FT-IR, thermal analysis and fluorescence characterization. The flexible coordination modes of PPAA⁻ are also briefly analyzed. The flexible coordination modes of PPAA⁻ and benzenedicarboxylate isomers also reveal great potential in the construction of these novel mixed-ligand luminescent frameworks with diverse structural motifs and unique functional properties.     

An unprecedented (4, 8)-connected self-penetrating Cu(I)-MOF constructed from the rare [Cu4I2]2 + cationic cluster and in situ generated tetrazole ligand

The in situ hydrothermal reaction of CuI, NaN₃ and 4-(1H-imidazol-1-yl)benzonitrile leads to a new three-dimensional pillared-layer Cu(I)-MOF, [Cu₂(μ₃-I)(μ₅-IPT)]_n (1) (HIPT = 5-[4-(imidazol-1-yl)phenyl]tetrazolate). Interestingly, the structure of 1 exhibits an unprecedented binodal (4, 8)-connected three-dimensional self-penetrating framework first constructed from [Cu₄I₂]^2 + cationic clusters as 8-connected nodes and in situ generated IPT ligands as 4-connected nodes. Moreover, 1 is strongly luminescent with green emission (λ_em = 545 nm) in the solid-state.     

Divalent cobalt,zinc, and copper coordination polymers based on a new bifunctional ligand: Syntheses,crystal structures,and properties

Three new coordination polymers, namely, [ML(H₂O)]_n (M = Co (1), Zn (2)) and [CuL(DMF)]_n (3), have been hydrothermally synthesized through the reaction of bifunctional ligand 5-((2-methyl-1H-imidazol-1-yl)methyl)benzene-1,3-dioic acid (H₂L) with divalent cobalt, zinc and copper salts, and structurally characterized by elemental analysis, IR and X-ray diffraction. Both complexes 1 and 2 are two-fold interpenetration 3D frameworks. Complex 3 exhibits (3,6)-connected framework with (4.6²)₂(4².6¹⁰.8³) topology. Furthermore, UV–vis absorption spectra and powder X-ray diffraction (PXRD) were investigated as well.     

Trinuclear Ru(II) polypyridyl complexes as human telomeric quadruplex DNA stabilizers

Two new trinuclear ruthenium(II) complexes [(bpy)₆Ru₃(tpbip)]⁶⁺ (1) and [(bpy)₆Ru₃(tptaip)]⁶⁺ (2) (bpy = 2,2′-bipyridine, tpbip = 1,3,5-tris(1,10-phenanthroline-[5,6-d]imidazol-2-yl)-benzene, tptaip = 2,4,6-tri(1,10-phenanthroline-[5,6-d]imidazol-2-yl)-1,3,5-triazine) have been synthesized and characterized. The interaction of human telomeric DNA with Ru(II) complexes was explored by means of CD spectroscopy, fluorescence titration, ITC and FRET melting. Results indicated that two complexes not only induce a remarkable conformational change of human telomeric DNA, but also have the ability to stabilize the G-quadruplex.     

Ru(II)–CO complexes of thioarylazoimidazoles: Syntheses,structures, spectroscopy and DFT calculation

The complexes, cis-(CO)-trans-(Cl)-[Ru(SRaaiNR)(CO)₂Cl₂] (2) and trans-(Cl)-[Ru(SRaaiNR)(CO)Cl₂] (3) (SRaaiNR = 1-alkyl-2-{(o-thioalkyl)phenylazo}imidazoles; R = Me (1a) and Et (1b)) have been synthesized and characterized. The structural confirmation is achieved by single crystal X-ray structure determinations. The complexes show Ru(III)/Ru(II) couple and ligand reductions. Electronic structure and spectral properties of the complexes have been explained with the DFT and TDDFT calculation.     

Syntheses,crystal structures,and magnetic studies of two cobalt(II) coordination polymers based on concurrent ligand extension

An ether bridged tetracarboxylic acid ligand, 5-(3′,4′-Dicarboxylphenoxy)-isophthalic acid (H₄L) was used to construct two Co(II) coordination polymers in presence of different nitrogen donor ligands such as 4,4′-bipyridine (4,4′-bpy) and 4,4′-bis(pyrid-4-yl)biphenyl (bpbp). The products formed under hydrothermal conditions are formulated as [Co₂L(4,4′-bpy)₂(H₂O)₃]_n (1) and {[Co(bpbp)₂(H₂L)]·H₂O}_n (2). The compounds were characterized by single-crystal X-ray diffraction, IR spectroscopy, elemental analysis, and powder X-ray diffraction (PXRD) measurement. Compound 1 shows an intriguing (3,4,5)-connected 3D framework with a point symbol of (4² · 6² · 8²)(4² · 6⁵ · 8³)(6² · 8). Compound 2 is an unusual 3D supramolecular framework generated by the one-dimensional [Co(bpbp)(H₂L)]_n polymer chain. The magnetic properties of compounds 1 and 2 were examined, indicating antiferromagnetic interactions between the cobalt(II) ions in the temperature range of 2–300 K.