Improved photovoltaic performances of Ru (II) complex sensitized DSSCs by co-sensitization of carbazole based chromophores

Herein, we report photovoltaic performance studies of three carbazole based dyes (N_1–3) derived from (Z)-3-(9-hexyl-9H-carbazol-3-yl)-2-(thiophen-2-yl)acrylonitrile scaffold as effective co-sensitizers in Ru (II) complex, i.e. NCSU-10 sensitized DSSCs. From the results it is evident that, the device fabricated using co-sensitizer N₃ with 0.2 mM of NCSU-10 exhibited improved photon conversion efficiency (PCE) of 8.73% with J_SC of 19.87 mA·cm^− 2, V_OC of 0.655 V and FF of 67.0%, while N₁ displayed PCE of 8.29% with J_SC of 19.75 mA·cm^− 2, V_OC of 0.671 V and FF of 62.6%, whereas NCSU-10 (0.2 mM) alone displayed PCE of 8.25% with J_SC of 20.41 mA·cm^− 2, V_OC of 0.667 V and FF of 60.6%. However, their EIS studies confirm that, N₁, showing higher V_OC is efficient in suppressing the undesired charge recombination in DSSCs through enhanced surface coverage on TiO₂ and thereby resulting in longer electron lifetime than that of NCSU-10 dye alone. Here, the higher PCE of N₃ can be attributed to its improved light harvesting efficiency, which is due to the presence of highly electron withdrawing barbituric acid in its structure. Conclusively, the results showcase the potential of simple carbazole based dyes as co-sensitizers in improving efficiency of DSSCs.     

Cobalt(II) complex containing two-ring scorpionate-like ligands formed in situ. Studies on the [Co0–1-hydroxymethyl-3,5-dimethylpyrazole–MoO3–NH4I] system

We report preparation and characterization of a novel complex cis–mer [Co(L)₂]I₂ CH₃OH (1) (L-N,N-bis(1-(3,5-dimethylpyrazolylmethyl)amine)) isolated from the [Co⁰–1-hydroxymethyl-3,5-dimethylpyrazole–MoO₃–NH₄I] system. A two-ring scorpionate ligand (L) was obtained in situ via redox and condensation processes. The catalytical properties of MoO₃ are responsible for the formation of this atypical scorpionate ligand. Compound (1) crystallizes in the orthorhombic space group Pna2₁ with a = 24.5578(14) Å, b = 13.8388(8) Å, c = 9.6072(7) Å, V = 3265.0(4) Å³ and Z = 4. The metal ion coordinates through six nitrogen atoms which belong to two tridentate ligands forming a deformed octahedron. The complex was characterized by IR, FIR, UV–VIS and magnetic investigations. The ligand was ranked in the spectrochemical series between imidazole and bipyridine. The crystal field splitting of tridentate N-donor L was found to be smaller in comparison to e.g. bidentate bipyridine.     

A homochiral Cu(II) coordination polymer built from helical motif based on two V-shaped ligands

By using a V-shaped N-containing ligand and a V-shaped carboxylate ligand, we have successfully synthesized a 3D novel copper homochiral coordination polymer, namely [Cu(OPY)(1,3-bdc)]_n (complex 1), [1,3-H₂bdc = isophthalic acid, OPY = 4,4′-(oxybis(4,1-phenylene))dipyridine]. The compound has been solvothermally synthesized and characterized by IR, elemental analysis, single crystal X-ray diffraction, XRD, UV–vis, and TG analysis. The complex 1 crystallizes in the chiral space group P6₅ and possesses an unprecedented uninodal 3D 7⁵∙ 8 topology. However, the complex was synthesized by achiral materials. The complex 1 displays a moderate SHG response and its SHG efficiency is about 0.3 times that of urea. In addition, the compound shows high thermal stability.     

One-dimensional supramolecular assembly of an Mn12 single molecule magnet by ligand interactions

A new Mn₁₂ complex was synthesized using ligand substitution reaction of Mn₁₂–OAc with 4-(thiophen-3-yl)benzoic acid and complex’s structural and magnetic properties were analysed. [Mn₁₂O₁₂(O₂CC₆H₄C₄H₃S)₁₆(H₂O)₃]·14CH₂Cl₂ (1) crystallized in the P2₁/c space group. Intermolecular π–π interactions between phenyl and thiophene rings of two adjacent Mn₁₂ molecules result in one-dimensional supramolecular assembly of 1 in the crystal. On the other hand, steric repulsion between the neighbouring molecules causes unusual ligand arrangement and coordination geometry of Mn(III) ion with five coordination. The ac magnetic study of 1 gives U_eff = 69.98 K and 1/τ₀ = 1.456 × 10⁸ s^?1 and dc reduced magnetization measurement gives S = 10, g = 1.95 and D = ?0.425 cm^?1 showing that outer ligand distortion has little effect on the magnetic properties.     

A lead(II)-orotate coordination polymer with a new coordination mode: Synthesis,structure and luminescent property

A lead(II) orotate complex [Pb(HOr)(H₂O)]_n (1), (H₃Or = orotic acid) was synthesized under hydrothermal condition and characterized by X-ray diffraction, IR, solid-state photoluminescence and thermogravimetric analysis. Lead atom in 1 is in a holodirected eight-coordinated polyhedron and the orotate ligand exhibits a new and unique hexametallic coordination mode. The lead complex shows a 6,6-connected (4⁸, 6⁶, 8)(4¹³, 6²) topology. The complex exhibits photoluminescence at 546 nm (λ_ex = 350 nm).     

A chiral mononuclear DyIII complex with field-induced single molecule magnet behavior

A chiral mononuclear Dy^III complex, formulated [Dy(PNO)₆(H₂O)₂]Cl₃ (1) (PNO = pyridine-N-oxide), has been prepared by using an achiral ligand through spontaneous resolution. Structure analyses show that complex 1 consists of a Dy^III mononuclear unit and such units interact with each other by hydrogen bonds to form helical chains along a axis. The crystals of 1 are optically active and opposite Cotton effects can be observed in the circular dichroism (CD) spectra. Magnetic studies reveal that complex 1 exhibits field-induced single molecule magnet behavior with an energy barrier of 49 K.     

One-dimensional macrocyclic zinc(II) coordination polymer containing an unusual bis-monodentate oxalate bridge

A new zinc(II) complex, {[Zn(L1)(oxalate)] · 3.5H₂O}_n (1) (L = 5,16-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0^1,18.0^{7, 12}]docosane) has been prepared and characterized by single crystal X-ray structure determination. In 1 the rigidity and steric hindrance of the macrocycle L1 causes the bridging oxalate ligand to coordinate to the zinc(II) ions in an unusual twisted bis-monodentate coordination (1,1′-bicoordination) mode.     

Hetero-trinuclear near-infrared (NIR) luminescent ZnLn2 (Ln = Nd,Yb or Er) complexes based on monomer ZnL Schiff-base precursor and o-vanillin

With the monomer [Zn(L¹)(H₂O)] (1) complex in situ formed by the deprotonated hexadentate Salen-type Schiff-base ligand H₂L¹ (H₂L¹ = N,N′-bis(3-methoxy-salicylidene)cyclohexane-1,2-diamine) and Zn(NO₃)₂ as the precursor, series of the hetero-trinuclear ZnLn₂ complexes [ZnLn₂(L¹)₂(L²)(NO₃)₂Cl] (Ln = Nd, 2; Ln = Yb, 3; Ln = Er, 4 or Ln = Gd, 5) were obtained from the further reaction with LnCl₃ (Ln = Nd, Yb Er or Gd) and the second o-vanillin (HL²) ligand, respectively. The photophysical properties of complexes 2–4 showed that the characteristic near-infrared (NIR) luminescence of Ln^3 + ions with two emission centers and emissive lifetimes in microsecond ranges, was sensitized from the excited state (both ¹LC and ³LC) of mixed H₂L¹–HL² ligands.     

A Michael-type reaction between acrylato ions and ethylenediamine coordinated to Ni(II). Synthesis,crystal structure and magnetic properties of [Ni2(EDDP)2(H2O)2] · 2H2O (H2EDDP = ethylenediamine-N,N-dipropionic acid)

The reaction between NiCO₃ · Ni(OH)₂, acrylic acid and ethylenediamine in a 2:4:1 molar ratio affords the binuclear complex, [Ni₂(EDDP)₂(H₂O)₂] · 2H₂O 1. The organic ligand, EDDP^2? (the dianion of the ethylenediamine-N,N-dipropionic acid ligand), results from the addition of one amine group to the carbon–carbon double bonds of two acrylato ions. The crystal structure of 1 consists of neutral centrosymmetric entities, with the nickel ions connected by two carboxylato groups, each one acting as a monoatomic bridge. The intramolecular Ni?Ni distance is 3.212 Å. The metal ions exhibit an octahedral geometry. The cryomagnetic investigation of 1 reveals an antiferromagnetic coupling of the nickel(II) ions (J = ?21.8 cm^?1, H = ?JS_Ni1S_Ni2).     

Supramolecular assembly of 1,3-diaminopropane and its unusual conversion by macrocyclic nickel(II) complex

The reaction of macrocyclic nickel(II) complex [NiL](ClO₄)₂ (1) with 1,3-diaminopropane affords a novel complex with the formula [NiL(a.a.)₂](ClO₄)₂ (2), where L = 3,10-bis(2-hydroxyethyl)-1,3,5,8,10,12-hexaazacyclotetradecane, a.a. = H₃N⁺(CH₂)₄COO⁻(5-aminovaleric acid ion), which reveals that the organic ligand 1,3-diaminopropane is converted during the process of the reaction.     

Studies on interaction of Cr(III) polypyridyl complexes with DNA

Two chromium(III) complexes containing derivatives of 1,10-phenanthroline were synthesized and characterized using different spectroscopic methods. The interaction of the synthesized complexes with DNA was performed. From the absorption titration data, the binding constant for the complexes [Cr(imiphen)₂Cl₂]⁺ (1) and [Cr(furphen)₂Cl₂]⁺ (2) with DNA were found to be 5.69 ± 0.3 × 10⁴ M^− 1 for 1 and 3.7 ± 0.2 × 10⁴ M^− 1 for 2, respectively. The viscosity studies show that both the complexes bind to DNA in a partial intercalative mode. The results of competitive binding assay reveal that both complexes displace EB from DNA marginally. Gel electrophoresis data show that both the complexes 1 and 2 requires co-reagent to induce DNA cleavage but complex 2 exhibit better nuclease activity compared to complex 1. The results from this study describe the role of ligand structure in the binding and cleavage of DNA as furan based ligand exhibit better cleaving ability compared to imidazole moiety.     

A novel 3D Co(II) coordination polymer with a considerable 2D channel: Synthesis,topological structure,magnetic and electrochemical properties

A novel 3D Co(II) complex [Co(Hhmt)(H₂O)∙H₂O] (1) (H₃hmt = 3,5-bis (hydroxymethyl)-1,2,4-triazole) has been hydrothermally synthesized. X-ray single crystal diffraction experiment reveals that each Hhmt^2 − ligand connects three Co(II) ions to form a 3D lvt topological framework with the (4² ∙ 8⁴) point symbol, especially for the existence of a considerable 2D channel. The magnetic and electrochemical properties of 1 are also discussed.     

A cobalt complex of a pentadentate aminopyridine ligand as an efficient catalyst for photocatalytic hydrogen generation

A linear pentadentate aminopyridine ligand 2,6-bis[(methyl(pyrid-2-ylmethyl)amino)-N-methyl]pyridine (Py^Mepam) has been prepared and characterized. This ligand readily coordinates with Co(II) or Zn(II) ions, and the resulting complexes of general formula [M(Py^Mepam)](BF₄)₂ (M = Co (1) and M = Zn (2)) have been thoroughly characterized and investigated for electro- and photocatalytic water reduction in acetonitrile. Electrochemical studies reveal that the complex 1 is active for electrocatalytic water reduction in acetonitrile. Under visible-light irradiation (λ > 400 nm), the complex 1 displays hydrogen evolution activity when in presence of [Ir(ppy)₂(bpy)]PF₆ as photosensitizer and triethylamine (TEA) as electron donor, whereas 2 shows negligible catalytic activity under the same conditions. Highest turnover numbers (TONs) of 290 for H₂ evolution are achieved from an optimized system containing 1 (0.1 mM), [Ir(ppy)₂(bpy)](PF₆) (0.5 mM), and 10 vol% TEA in CH₃CN-H₂O (1/1, v/v) mixed solvents at pH 10.     

Syntheses,structures and properties of novel d10 coordination polymers based on 4-[(1H-imidazol-4-yl)methylamino]benzoic acid ligand

Complete and partial deprotonation of new ligand 4-[(1H-imidazol-4-yl)methylamino]benzoic acid (H₂L) under hydrothermal conditions lead to the formation of two novel coordination polymers [ZnL]_n (1) and [Ag(HL)]_n (2). Complex 1 displays a rare three-dimensional (3,6)-connected rtl framework with (4 · 6²)₂(4² · 6¹⁰ · 8³) topology, while 2 has a one-dimensional chair-like structure including significant argentophilic Ag–Ag interactions. Both 1 and 2 show remarkable thermal stability and complex 1 was found to show strong blue luminescence with emission maxima at 381 nm upon excitation at 347 nm in the solid state at room temperature.     

Synthesis,structure, and electrochemical behavior of a new dinuclear Rh(III) complex bridged by a bpp− ligand (bpp− = 3,5-bis(2-pyridyl)pyrazolate)

The new dinuclear rhodium complex [(Cp*RhCl)₂(bpp)](PF₆) ([1](PF₆), Cp* = pentamethylcyclopentadienyl, bpp = 3,5-bis(2-pyridyl)pyrazolate) was synthesized by the reaction of [Cp*RhCl₂]₂ with 3,5-bis(2-pyridyl)pyrazole (bppH). [1](PF₆) was characterized by ¹H- and ¹³C{¹H}-NMR spectroscopy and X-ray diffraction. The distance between the two Rh atoms in [1](PF₆) is 4.746(3) Å. A cyclic voltammogram of [1](PF₆) in acetonitrile shows three-step reduction peaks at E_pc = − 1.44, − 1.68 and − 1.88 V (vs. Fc⁺/Fc), which are assigned to the reduction of the two Rh(III) centers and the bpp⁻ ligand, respectively. [1](PF₆) catalyzes the reduction reaction of NAD⁺ (nicotinamide adenine dinucleotide) using HCO₂⁻ as a reductant.     

A new cyclic binuclear Ni(II) complex as a catalyst towards nitroaldol (Henry) reaction

A new cyclic binuclear Ni(II) complex, [Ni₂(H₂L)₂] · 4MeOH (1), has been synthesized using the Schiff base N′¹,N′³-bis(2-hydroxybenzylidene)malonohydrazide (H₄L). The X-ray crystal structure of 1 shows that the ligand coordinates in the dianionic keto form (H₂L^2 −) via mutual sharing of two Ni(II) ions. Complex 1 acts as a heterogeneous catalyst for the Henry reaction in water. A maximum conversion of ca. 93% was obtained under optimized conditions.     

Design,synthesis, crystal structure and photophysical studies of an emissive,terbium based sensor for zinc

The synthesis, crystal structure and photophysical studies of the probe complex Tb · L are described. Tb · L is a mononuclear complex with a 46-membered macrocyclic rings constructed by intermolecular hydrogen bond. The mononuclear complex Tb · L shows Laporte-forbidden ⁵D₄ → ⁷F_J f–f transitions and exhibits strong green luminescence emission bands in the solid state at ambient temperature which is characteristic of terbium ion. New selective luminescent lanthanide chemosensor for Zn(II) ion based on Tb · L is also described, suggesting host–guest complexation signaling transduction mechanism.     

Synthesis and characterization of an unprecedented 3D lanthanide coordination polymer assembled by cubane-like clusters and a flexible V-shaped dicarboxylate ligand

A lanthanide coordination polymer based on H₂sfdb ligand, namely [Tb₄(sdbc)₄(phen)₂(μ₃-OH)₄]_n ∙ 1.5nH₂O (1) (H₂sfdb = 4,4′-sulfonyldibenzoic acid, phen = 1,10-phenanthroline) has been hydrothermal synthesized and characterized. Compound 1 exhibits an unprecedented three-dimensional framework that comprised new cubane-like hydroxo clusters [Tb₄(μ₃-OH)₄]^8 + as the nodes and flexible (sfdb)^2 − ligands as the linkers. In 1, (sfdb)^2 − ligands display completely different four kinds of coordination modes. Interestingly, not only the carboxylate groups but also one oxygen atom of sulfonyl group of (sfdb)^2 − ligand are coordinated with Tb^III ions in 1, which is first found in the compounds based on H₂sfdb ligand. The luminescence experiments show that Tb^III compound exhibits the typical Tb^III-centered luminescence.     

A helical salicyladoxime-based manganese triangle chain with single-molecule magnet behavior

The reaction of 2-hydroxyphenylpropanone oxime (Et-H₂salox) with Mn(NO₃)₂·4H₂O, NEt₃ and 1,3-bis(4-pyridyl)propane-N,N′-dioxide (bppo) in EtOH/H₂O mixture afforded a one-dimensional coordination polymer with the formula [Mn₃O(Et-salox)₃(bppo)(MeOH)(H₂O)₃](NO₃)_0.5(Et-Hsalox)_0.5·MeOH·H₂O (1·MeOH·H₂O). 1·MeOH·H₂O had a manganese triangle structure, [Mn^III₃O]^7 +, which was used as a building unit for a subsequent assembly of an oximate and central oxide. The flexible bppo ligand linked the units, resulting in the formation of a 1D helical structure. Variable temperature direct current magnetic susceptibility measurements of complex 1·MeOH·H₂O were carried out. Exchange interactions of the metal centers of complex 1·MeOH·H₂O were examined, and the results indicate that both ferro- and antiferromagnetic interactions simultaneously coexist in 1·MeOH·H₂O, resulting in an S = 2 ground state. Moreover, complex 1·MeOH·H₂O shows the frequency dependence of the out-of-phase component in alternating current magnetic susceptibility measurements, indicating single-molecule magnet behavior with U_eff = 28 K and τ₀ = 1.8 × 10^− 9 s.     

Tuning structural topologies of two coordination polymers via alter N-donor auxiliary ligand

Based on the N-donor auxiliary ligand effect, two new Ni(II) coordination polymers [Ni₂(HL)₂(bpe)₂] (1) and [Ni(HL)(bipy)(H₂O)₂] (2) [H₃L = 2-(4′-carboxyphenyl)terephthalic acid; bpe = 1,2-bis(4-pyridyl)ethane; bipy = 4,4′-bipyridine] have been successfully synthesized and characterized by single-crystal X-ray diffraction study, elemental analysis, IR spectra, TGA and powder X-ray diffraction (PXRD). This work presents a comparative study on the tuning of structural topologies by using two N-donor ligands with different lengths as auxiliary ligands. The structural determination reveals that complex 1, incorporating bpe ligands, features a three-dimensional (3D) 4-connected 4-fold dia interpenetrating architecture with the point symbol of 6⁶, while 2, containing bipy ligands, exhibits a two-dimensional (2D) sql layer structure with a 4-connected (4⁴·6²) topology. Moreover, the magnetic properties for 1 and 2 were also measured and compared on account of their different structures.