Search

Polycrystalline semiconductor films of BiCdTe composites were electro-deposited on ITO coated glass through a voltammetric technique under variable periodic cycles. The crystal structure and composition of the films were determined by X-ray diffraction, scanning electron microscopy, atomic force microscopy and energy dispersive X-ray analysis and the optical features were recorded using a UV-visible spectrometer. The band gap energy of the ternary films was found to be within the range of 1.5–1.7 eV. Electrochemical impedance spectroscopy provided important information regarding the interfacial properties of the films in polysulphide medium. The current–voltage measurements for the photo-electrochemical solar cells fabricated with the prepared films as anode components exhibited encouraging photo-response and improved functional properties. The BiCdTe composite films were further subjected to anodic corrosion studies followed by anodic stripping voltammetry and the stability of the films was compared with that of CdTe. An optimal composition of the film matrix shows a performance efficiency of 4.3%, significantly high photo current and considerably greater stability compared to the individual binary chalcogenide films. [ABSTRACT FROM AUTHOR]

Two novel complexes [Mn 2 (phmp) 2 ](ClO 4 ) 2 ( 1 ) and [Ni 2 (phmp)(μ-H 2 O)(H 2 O) 4 ](NO 3 ) 3 ( 2 ) were synthesized using an “end-off” compartmental ligand [H-phmp = 4-Methyl-2,6-bis-(pyridin-2-yl-hydrazonomethyl)-phenol] with Mn(II)-perchlorate and Ni(II)-nitrate salts as metal precursors. Both these complexes were characterized by spectroscopic (IR, UV–Vis) and X-ray crystal structure analysis. The ligand, H-phmp acts as a pentadentate NNONN donor for both the metal complexes and the geometry of the complexes 1 and 2 is distorted octahedral. The DFT optimized bond distances and angles are well correlate to the X-ray structure bond parameters. For complex 1 the transitions at 435 nm and 428 nm have mixed MLCT ( dπ (Mn) → π * (L)) and ILCT ( π (L) → π * (L)) character whereas other transitions correspond to intra-ligand charge transfer transitions (ILCT). For complex 2 , weak transitions at 464 and 405 nm correspond to ligand to metal charge transfer transitions (LMCT) ( π (L) → dπ (Ni)) and most of the other transitions have ILCT character. As anticipated, various weak forces, i.e. anion–π/π–anion/anion–π/π–NH interactions as well as C–H/π interaction, play a key role in stabilizing the self-assembly process observed for both compounds. [ABSTRACT FROM AUTHOR]

The well known rhodamine framework offers an ideal model for the development of fluorescence enhanced chemosensors. Herein, a novel and simple molecule chemosensor, (E)-2-((benzo[d][1,3]dioxol-4-ylmethylene)amino)-3′,6′-bis(diethylamino)spiro[isoindoline-1,9′-xanthen]-3-one ( L ), has been designed by combining a rhodamine B hydrazide and a benzo[d][1,3]dioxole-4-carbaldehyde in a single molecule to prove the selectivity and sensitivity for Al 3+ and Cr 3+ in a dual-channel mode (fluorescence emission and UV–Vis). The signal transduction occurred by the increase of conjugation in the ring-open form than in the ring-closed form. Furthermore, the chemosensor L could also be used as an imaging probe without cytotoxicity for uptake and detection of Al 3+ ion in HeLa cells. [ABSTRACT FROM AUTHOR]

A novel fluorescent chemosensor based on a rhodamine derivative (L) was designed, synthesized, and used as a selective Al+3 ion sensor. Upon addition of Al3+ to an aqueous-acetonitrile solution of L, the development of a strong fluorescence signal by a chelation-enhanced fluorescence (CHEF) process was observed with an attractive glowing orange emission. This sensor shows high selectivity towards Al3+ ions in the presence of other competing metal ions. The fluorescence quantum yield of L–Al3+ (Φf = 0.30) was found to be very high compared to the bare ligand. The limit of detection (LOD) of Al3+ ions was calculated to be 2 × 10−8 M by fluorescence titration. The 1 : 1 binding stoichiometry of the metal complex was established by combined UV-vis, fluorescence and TOF-MS spectroscopy. [ABSTRACT FROM AUTHOR]

Highlights: [•] A new pyrimidine derived Schiff Base ligand (L) was synthesized. [•] One zinc (1) and one cadmium (2) complexes have been synthesized and characterized. [•] The geometries of both complexes were optimised in the singlet state by DFT method. [•] TDDFT calculations have been performed. [•] Complex 1 exhibits intraligand 1(π→π∗) fluorescence. [ABSTRACT FROM AUTHOR]

Abstract: A pyrazole based ditopic ligand 5(E)-5-methyl-N′-(pyridin-2-ylmethylene)-1H-pyrazole-3-carbohydrazide (PzOPyH), prepared by the reaction between 5-methylpyrazole-3-carbohydrazide and pyridine-2-carbaldehyde, reacts with Mn(ClO4)2·6H2O to form a self-assembled, antiferromagnetically coupled alkoxide bridged pentanuclear Mn(II) homoleptic cluster complex [Mn5(PzOPy)6](ClO4)4 (1). The complex has a central Mn5(μ-O6) core involving six ligand molecules. This pentanuclear core has a trigonal bipyramidal arrangement of Mn(II) atoms, where, the axial metal centers (Mn2 and Mn_2) have a N3O3 chromophore and the equatorial centers (Mn1, Mn_1 and Mn3) have N4O2 chromophore with distorted octahedral arrangement around the metal centers. Intramolecular antiferromagnetic interaction between Mn(II) centers (J =−1.42, S =5/2) is the signature of the molecule. [Copyright &y& Elsevier]

Abstract: Pyrazole based ditopic ligand HL1 ((Z)-N′-(5-methyl-1H-pyrazole-3-carbonyl) picolinohydrazonamide) reacts with Cd(ClO4)2·6H2O and Zn(ClO4)2·6H2O to form a self assembled pentanuclear Cd(II) complex [Cd5(L1)6](ClO4)4 (1) and a mononuclear Zn(II) complex [Zn(HL1)2](ClO4)2 (2). On the other hand, HL2 ((Z)-N′-(5-methyl-1H-pyrazole-3-carbonyl) pyrazine-2-carbohydrazonamide) also forms a mononuclear [Zn(HL2)](ClO4)2(MeOH)2 (3) with Zn(ClO4)2.6H2O. All these complexes have been characterized crystallographically and spectroscopically. The Cd(II) complex (1) has a pentanuclear core with trigonal bipyramidal arrangement of Cd(II) atoms, where, the axial metal centers (Cd2 and Cd5) have N3O3 chromophore and the equatorial centers (Cd1, Cd3 and Cd4) have N4O2 chromophore with distorted octahedral arrangement around the metal centres. In 2 and 3, the NNO donor ligand molecules in their ketoimine form produce distorted octahedral environment around the Zn(II) centre with N4O2 chromophore utilizing pyridine/pyrazine N, one azomethine N and one carbohydrazide O atoms. Here, the pyrazole ring N atoms remain silent in coordination process. On the other hand, in 1, the same ligand HL1 coordinates in its deprotonated imineol form and functions as N3O donor, while, the pyrazole N atoms take part in coordination process. Ligands HL1 and HL2 are fluorescence silent but complexes 1, 2 and 3 show considerable fluorescence. The fluorescence intensity of 1 is higher than that of 2 and 3. [Copyright &y& Elsevier]

Abstract: The pyrazole based ditopic ligand PzCAP (HL, 5-methyl-N′-(1-(pyridine-2-yl)ethylidene)-1H-pyrazole-3 carbohydrazide) reacts with Ni(ClO4)2·6H2O, Zn(ClO4)2·6H2O and Cd(ClO4)2·6H2O to form a new alkoxide bridged binuclear Ni(II) complex [Ni2(PzCAP)3](ClO4)3·6(H2O) (1), a mononuclear Zn(II) complex [Zn(PzCAP)2](ClO4)(H2O) (2) and a self assembled pentanuclear Cd(II) complex [Cd5(PzCAP)6](ClO4)4(H2O) (3). These complexes have been characterized crystallographically and spectroscopically. In complex 1, the three ligand molecules display variable denticity towards the Ni(II) centers, one ligand behaves as tetradentate and two others behave as tridentate ligands to create distorted octahedral environments around the two Ni(II) centers, with N5O and N4O2 chromophores. In 2, the same ligand, using keto and enolic oxygen atoms, produces a distorted octahedral environment around the Zn(II) center with a N4O2 chromophore. Complex 3 has a pentanuclear core with a trigonal bipyramidal arrangement of Cd(II) atoms, where the axial metal centers (Cd2 and Cd4) have N3O3 chromophores and the equatorial centers (Cd1, Cd3 and Cd5) have N4O2 chromophores, with distorted octahedral arrangements around the metal centers. Interestingly, the pyrazole unit remains inactive to coordination for complex 2, whereas this unit takes part in coordination for 1 and 3. The ligand HL, complex 2 and complex 3 show fluorescence, while in 1 the fluorescence is substantially quenched compared to the ligand (HL) and its Zn and Cd complexes. As the ligand is capable of using different binding modes, according to the demands of the complex, the emission properties also change accordingly. [Copyright &y& Elsevier]

Abstract: A pyrimidyl-pyrazole based ditopic ligand N-[amino(pyridin-2-yl)methylidene]-1-(4,6-dimethylpyrimidin-2-yl)-5-methyl-1H-pyrazole-3-carbohydrazonic acid, PymPzOAP prepared by the reaction between pyrimidyl pyrazole 3-carbohydrazide and methyl ester of iminopicolinic acid, reacts with Cu(NO3)2·6H2O to form a self-assembled, ferromagnetically coupled alkoxide bridged tetranuclear homoleptic Cu(II)4 [2×2] grid complex [Cu4(PymPzOAP)4](NO3)4 (1). The complex has a central Cu4(μ-OR)4 core involving four ligand molecules. All the Cu(II) centers have N4O2 coordination environment with distorted octahedral geometry. Intramolecular ferromagnetic interaction between Cu(II) centers (J =4.94, S =4/2) is the signature of the molecule. [Copyright &y& Elsevier]

Abstract: A binuclear acylhydrazine bridged Cu(II) complex, [Cu2(L)(NO3)3(H2O)] (1), and an anti-orthogonal binuclear oxovanadium(V) complex, [V2O4(L)2] (2), have been synthesized and characterized spectroscopically and crystallographically. The ligand HL has two potentially bridging functional groups (μ-O, μ-N–N) and consequently can exist in the following coordination conformers: (a) metal centers bridged by μ-O, (b) metal centers bridged by μ-N–N. A rare acylhydrazine bridged (a) type configuration exists in the dinuclear Cu(II) complex 1. The bridging ligand mediates a strong antiferromagnetic coupling (J =−99cm−1). The exchange pathway parameters have also been evaluated from density functional theoretical calculations to corroborate the bridging signatures with experimental findings (J =−93.96cm−1). Molecule 2 has a centrosymmetric structure with each vanadium center having a distorted octahedral geometry. It shows a one step irreversible reduction at +0.43V. The bond angles, bond lengths and torsion angles in 2 are correlated with DFT. [Copyright &y& Elsevier]

Abstract: Two new dinuclear copper(II) complexes [Cu2(PymPz)2(N3)2Cl2] (1), [Cu2(PymPz)2(N3)4] (2) and two new dinuclear cobalt(II) complexes [Co2(PymPz)2Cl4] (3), [Co2(PymPz)2(N3)4] (4) [PymPz=2-(3,5-dimethyl-1H-pyrazol-1-yl)-4,6-dimethylpyrimidine] have been synthesized and characterized crystallographically and spectroscopically. In each of the complexes 1, 2 and 4 the two adjacent metal centers are bridged by a pair of μ-1,1 azide groups whereas in 3 the metal centers are bridged by a pair of chloride ions. In the complexes, all the metal centers are pentacoordinated. In 1 and 2 the copper(II) centers have distorted square pyramidal geometry (τ =0.18 for 1 and 0.091 for 2) but in 3 and 4 cobalt(II) centers have distorted trigonal bipyramidal geometry (τ =0.619 for 3 and 0.557 for 4). Complexes 1 and 2 show antiferromagnetic interaction (J =−7.09cm−1 for 1 and J =−17.00cm−1 for 2) whereas 3 and 4 show ferromagnetic interaction (J =7.44cm−1 for 3 and J =10.45cm−1 for 4). Complex 3 displays an unprecedented ferromagnetic interaction over double μ-chloro bridges in the observed angle range (94.87°). The exchange pathways parameters for all the complexes have also been evaluated from density functional theoretical calculations to corroborate the bridging signatures with experimental findings. [Copyright &y& Elsevier]

Four new azide bridged dinuclear Mn(II) complexes [Mn(L1)(μ1,1-N3)(N3)]2 (1), [Mn(L2)(μ1,1-N3)(N3)]2 (3), [Mn(L3)(μ1,1-N3)(N3)]2[(N3)Mn(L3)(μ1,1-N3)(N3)]2 (4) and [Mn(L4)(μ1,1-N3)(N3)]2[Mn(L4)(μ1,1-N3)(N3)]2 (5) and one new dicynamide bridged binuclear Mn(II) complex {[Mn2(L1)2(dca)2(H2O)2(μ1,5-dca)](ClO4)} (2) have been synthesized using the pyrimidine derived primary Schiff base ligands L n (n =1–4), with azide and dicynamide as bridging ligands. All the five complexes were characterized by elemental analyses, IR spectroscopy and single crystal X-ray crystallography, together with magnetic measurements of 1–4. The tridentate Schiff base ligands are the [1+1] condensation products of 2-hydrazino-4,6-dimethyl pyrimidine with 2-acetyl pyridine, pyridine-2-carbaldehyde, 2-benzoyl pyridine and di(2-pyridyl) ketone for L n (n =1–4), respectively. All the complexes except 2 contain Mn(II)-azido links in which the Mn(II) centres are bridged by a di-μ1,1-azido (double EO) group. The double EO bridging fragments in the complexes are similar with bridging angles (Mn–N–Mn) ranging from 102.59° to 104.81°. Magnetic property studies reveal that in 1, 3 and 4 intramolecular ferromagnetic interactions are mediated through the EO azido bridges with J parameters in the range 4.3–5.12cm−1, while a weak antiferromagnetic interaction prevails in 2 (J =−0.12cm−1) via μ1,5-dicynamide bridges. In addition, complexes 1, 3 and 4 show weak intermolecular antiferromagnetic interactions (J =−0.025 to −0.027cm−1). [ABSTRACT FROM AUTHOR]

Highlights: [•] Pyrimidine derived Schiff base ligand has been prepared. [•] Wide structural variety of complexes by the ligand was prepared. [•] IR, UV–Vis spectra support structural moiety. [•] Cd(II) complex is fluorescence active rather than other. [ABSTRACT FROM AUTHOR]

Abstract: The syntheses, crystal structures and photoluminescence properties of four new Cd(II) complexes are reported using strongly coordinating ligand 3,5-dimethyl-1-(2′-pyridyl) pyrazole (L) in presence of anionic ancillary bridging ligands as nitrite, chloride and dicyanamide. Among the complexes two (1 and 2) are monomeric, 3 is μ2 – chloro bridged dimer and the last one (4) is a mixed alternate chloro – end to end (EE) dicyanamide bridged 1D polymer. All the four complexes have been X-ray crystallographically characterized. The ligand L behaves as a potent bidentate neutral N, N donor. Geometrical diversity of Cd(II) complexes is due to no loss or gain of crystal field stability with the variation of geometry. Consequently the stability of a structure depends on steric requirements. The ligand L shows considerable fluorescence and all four complexes in methanol exhibit interesting photoluminescence properties with different emission intensities. The band maxima and fluorescence efficiency (in methanol) are found to be dependent on the coordination chromophore and structural rigidity induced by the incorporated Cd(II) ion. Among the synthesized complexes 1 exhibits the highest fluorescence intensity in methanol. [Copyright &y& Elsevier]

Abstract: One binuclear Cu(II) complex, [Cu2(L1)2(N3)2] (1), and a trinuclear Cu(II) complex, [Cu3(L2)3(μ1,1N3)2](ClO4) (2), of two potentially tridentate NNO-donor Schiff base ligands, [2-(1-(2-(4,6-dimethylpyrimidin-2-yl)hydrazono)ethyl)phenol] (HL1) and [2-((2-(4,6-dimethyl pyrimidin-2-yl) hydrazono) methyl) phenol] (HL2), have been synthesized and characterized by elemental analyses, UV–Vis IR spectroscopy, DFT and single crystal X-ray crystallography. The ligands HL1 and HL2 are [1+1] condensation products of 2-hydrazino-4,6-dimethylpyrimidine with 2-hydroxy acetophenone and salicylaldehyde respectively. In 1, the two Cu(II) centers are bridged by μ-phenoxo groups. In 2, the three Cu(II) centers are held together by two μ1,1 bridging azide ions and a phenoxo oxygen atom which binds the three metal centers and behaves as a μ3-O atom. The geometries of the complexes have been optimized using the UB3LYP level of theory. The calculation confirms that all the copper centers are five coordinate with distorted square pyramidal geometries, which is consistent with the experimental data. [Copyright &y& Elsevier]

Abstract: Three new dinuclear Cu(II) complexes, [Cu2(L)2(L1)]PF6 (1), [Cu2(L)2(L2)]PF6 (2) and [Cu2(L)2(L3)]PF6 (3), of a potentially tridentate NNO-donor Schiff base ligand [HL=2-(2-(4,6-dimethylpyrimidin-2-yl)hydrazono)methyl)phenol] and the ancillary ligands [HL1 =benzoic acid, HL2 =salicylic acid, HL3 =4-amino benzoic acid] have been synthesized and characterized by elemental analyses, IR, single crystal X-ray crystallography, spectroscopic, electrochemical and catalytic studies. The ligand HL is the [1+1] condensation product of salicylaldehyde with 2-hydrazino-4,6-dimethyl pyrimidine. In the complexes 1, 2 and 3, two Cu(II) centers are bridged by the carboxylic oxygen atoms of the respective acid moiety. All the metal centres have square-based pyramidal (SP) geometries (Γ =0.120, 0.124, 0.109 for 1, 2 and 3, respectively). The dinuclear Cu(II) complexes show high catalytic activity and selectivity for the epoxidation of styrene, cyclohexene and cyclooctene using tert-butyl hydroperoxide (TBHP) as the oxidant. [Copyright &y& Elsevier]

Abstract: One new dinuclear Zn(II) complex, [(N3)Zn(L1)(μ1,1-N3)]2 (1), and a dinuclear Cd(II) complex, [(N3)Cd(L1)(μ1,1-N3)]2 (2), of the potentially tridentate NNN-donor Schiff base ligand N-(4,6-dimethyl-pyrimidin-2-yl)-N′-(1-pyridin-2-yl-ethylidine)-hydrazine (L1) and another dinuclear Cd(II) complex [(NCS)Cd(L2)(μ1,3-NCS)]2 (3) of a similar NNN donor Schiff base ligand, N-(4,6-dimethyl-pyrimidin-2-yl)-N′-pyridin-2-ylmethylene-hydrazine (L2), have been synthesized and characterized by elemental analyses, IR, 1H NMR, fluorescence spectroscopy and single crystal X-ray crystallography. The fluorescence spectral changes observed upon addition of the Zn(II) ion to a mixture of L1 and azide showed high selectivity towards the Zn(II) ion over other metal ions. The ligands L1 and L2 are [1+1] condensation products of 2-hydrazino-4,6-dimethyl pyrimidine with 2-acetyl pyridine and pyridine-2-carbaldehyde, respectively. In the complexes 1 and 2 the two Zn(II) and Cd(II) centers are held together by μ1,1-bridged azide ions, while in 3 the two Cd(II) centers are bridged by μ1,3-thiocyanate ions. Complex 1 shows high chelation enhanced fluorescence compared to 2 and 3. All the metal centers have a distorted octahedral geometry. [Copyright &y& Elsevier]

The pyrazole based ligands (E)-2-(3,5-dimethyl-1H-pyrazol-1-yl)-N′-(pyridin-2-ylmethylene acetohydrazide (N-PzOPyH) and (E)-5-methyl-N′-(pyridin-2-ylmethylene)-1H-pyrazole-3-carbo hydrazide (PzOPyH), a 1:1 condensation product of 2-(3,5-dimethyl-1H-pyrazol-1-yl)aceto hydrazide and 5-methylpyrazole-3-carbohydrazide with pyridine-2-carbaldehyde respectively, and their keto oxygen bridged Cd(II) complexes [Cd 2 (N-PzOPy) 2 (H 2 O) 4 ](ClO 4 ) 4 ( 1 ), [Cd 2 (PzOPy) 2 (H 2 O) 4 ](ClO 4 ) 4 ( 2 ) and [Cd 2 (PzOPy) 2 (NO 3 ) 4 ] ( 3 )] are reported. They have been characterized structurally and spectroscopically. The potential tetradentate NONN-donor ligands N-PzOPyH and PzOPyH are engaged in the coordination around the cadmium(II) center through the nitrogen atoms of pyrazole, azomethine and pyridine and the ketonic oxygen atom of the carbohydrazide group to form complexes 1 , 2 and 3 , respectively. These ligands span themselves in the equatorial plane and the pentagonal bipyramidal geometry is completed around the metal centres (with an N 3 O 4 chromophore) with two apical water molecules (for 1 and 2 ) and with two nitrate ions (for 3 ). These keto bridged Cd(II) complexes are further stabilised by supramolecular interactions, like π⋯π, C–H⋯π and H-bonding interactions. [ABSTRACT FROM AUTHOR]