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Transparent optoelectronics devices have recently drawn considerable research attentions for the next generation electronic technologies. Here, we fabricate highly transparent (87 to 90% under visible light) composite films of graphene oxide (GO) and zinc oxide (ZnO) by all-solution process. The non-linear current–voltage characteristics at room temperature resemble Schottky barrier junction formation between ZnO-GO film surface and Ag dot. Under UV irradiation (λ ~ 375 nm and power density ~1 mW/cm2) the ideality factor increases from 7.82 to 8.72 but the potential barrier height reduces from 0.66 to 0.50 eV in ZnO and ZnO-GO 25% films which are favorable for advancing optoelectronic technologies. This is demonstrated by excellent UV photoresponsivity of 5.3 A/W at low bias (+1 V) for ZnO-GO 25% along with low UV response (15.8 s) and recovery times (36.6 s). While at −1 V bias the photoresponsivity reaches to 1.25 A/W. Such distinct characteristics as compared to other reports on all-solution processed ZnO-GO composites could be attributed to the reduction of GO to form rGO within ZnO matrix to develop conducting channels in the composite films, the formation of excellent Schottky barriers with Ag, the modulation in excitonic characteristics by defect distributions at the interfacial regions among rGO flakes and ZnO matrix, and the facilitated charge transport through the junctions.

All solution processed transparent thin films of graphene oxide (GO) and zinc oxide (ZnO) in different compositions prepared by a simple two-step chemical synthesis method have been studied for their UV detection properties. The preparation of GO through oxidation of graphite flakes is followed by sol–gel spin coating deposition of the GO–ZnO composite films on glass substrates. The surface morphology, microstructure and composition of the samples have been studied to confirm the formation of composite thin films comprising wurtzite-ZnO nanocrystallites and GO flakes. Optical studies demonstrate that both the transparency and optical band gap of the samples as estimated from wavelength dependent transmittance curves decrease with the increase of GO content in the films, while the charge carrier concentration increases by 5 fold. The in-plane current–voltage (I–V) measurements with two silver electrodes on the GO–ZnO film show a significant enhancement of the photosensitivity in comparison to ZnO films when they are exposed to UV light of different intensities. The response time (t90-response) is nearly three times smaller for GO–ZnO composite films as compared to that of pure ZnO. This improvement is attributed to the defect state modulation and carrier density improvement of the thin films with incorporation of GO, which is encouraging to propel optical, electrical and hence optoelectronics applicability of ZnO composite based transparent devices.

Herein, we report the formation of a unique water-chloride-methanol 2D supramolecular network within the hydrophobic interlayer cavities of a novel flexible metal–organic supramolecular host (MOSH) framework formed by π-induced self-assembly of the monomeric metal–organic complex [Pr(1,10-phen)2(H2O)5]Cl3(H2O)(CH3OH) (1,10-phen = 1,10-phenanthroline) (complex 1). Single crystal X-ray diffraction (SC-XRD), powder X-ray diffraction (PXRD) and spectroscopic techniques are used to characterize the complex. The structural analysis reveals that in this MOSH the discrete metal–organic moieties are connected by π⋯π interactions to form 2D metal–organic supramolecular sheet structures. The guest water and methanol molecules together with counter chloride anions stabilize in the MOSH framework through hydrogen bonding interactions between the 2D metal–organic supramolecular layers. The hydrogen bonding interactions among the coordinated water and guest species form a unique 2D supramolecular water-chloride-methanol sheet structure. Upon removal of guest water and methanol molecules by heat treatment the supramolecular framework gets shrunk but retains the crystallinity while upon re-absorption of water molecules it undergoes structural change with expansion of effective guest accessible void space. The flexibility of the supramolecular framework and the mechanism of thermally induced phase transformation in the MOSH are examined by PXRD study. The photoluminescence property of the complex 1 and the crystalline complex obtained after rehydration has been thoroughly investigated. The theoretical analysis has been performed to resolve the issue of stability of the 2D supramolecular water-chloride-methanol sheet in the MOSH framework and it has been found that for complex 1 the stabilization energy of the [(H2O)6-(CH3OH)-Cl3]n3− is 1949.427Kcal mol−1.

The design of pharmaceutical cocrystals has become a prime thrust of crystal engineering and the pharmaceutical industry in recent times – but the use of pharmaceutical cocrystals as regular drugs is yet to be explored. Quinoxaline acts as a basic skeleton of several potential anticancer drugs. We have successfully cocrystallized quinoxaline with another organic molecule 3-thiosemicarbano-butan-2-one-oxime (TSBO, a virus replication inhibitor) and examined the anticancer activity of the cocrystal. The crystal structure of the cocrystal was determined by single crystal X-diffraction study. According to thermogravimetric study the cocrystal exhibits better thermal stability than quinoxaline. UV-Vis spectroscopic study has shown that in solution state the behavior of the cocrystal and the physical mixture of its components (mixture of quinoxaline and TSBO) are significantly different. The solubility of the cocrystal in distilled water has been found to be 31.9 mg mL−1. The cocrystal exhibits a specific cytotoxic effect on lung cancer cells (A549) at 10−7 M concentration while it shows growth inhibitory effect on normal cells. The detailed mechanistic study of the cytotoxicity of the cocrystal suggests that it follows the mitochondrial mediated cell death pathway through activation of Caspase 9 and Bax. It also shows anticancer activity on breast cancer cells (MCF-7).

Two co-crystals of 2,3-dimethylquinoxaline (DMQ) and dimethylglyoxime (DMG) have been synthesized and characterized by single crystallographic X-ray, IR and thermal studies. Co-crystal I is colorless while co-crystal II is orange in color. In the co-crystals, both hydrogen-bonding and π··· interactions assemble both DMQ and DMG within the crystal structure. For co-crystal I, 2D supramolecular sheet structure is formed by utilizing both hydrogen bonding and π··· interactions, while for co-crystal II supramolecular 1D chain motifs are formed by O–H···N hydrogen bonding interactions which are held together by C–H···O interactions to form 2D supramolecular network. These 2D supramolecular networks are further stacked by π···π and C–H···π interactions of aromatic rings of DMQ leading to the formation of 3D supramolecular structure. Examination of the intermolecular interactions and crystal packing via Hirshfeld surface analysis reveals that most of the close contacts are associated with weak interactions. The fingerprint plots indicate that these weak interactions have significant role in crystal packing. Thermogravimetric analyses of the co-crystals have been carried out. Two concomitant co-crystals of active pharmaceutical ingredients (API) 2,3-dimethylquinaxoline (DMQ) and co-crystallizing agent dimethylglyoxime (DMG) have been synthesized and characterized by X-ray crystal structure, IR analysis along with their detailed Hirshfeld surfaces analyses.

The nonlinear optical active chiral complex 1 [{Co(2,5-pdc)(H2O)2}H2O]n (2,5-pdc = 2,5-pyridine dicarboxylate) has been synthesized via a solvothermal technique using the achiral 2,5-pdc ligand. Complex 1 (phase 1), a two-dimensional coordination polymer, undergoes crystalline to amorphous (phase 2) transformation upon deaquation, which under reaquation generates a new microcrystalline phase (phase 3). The crystal structure of phase 3 has been determined by powder X-ray diffraction analysis (PXRD), which reveals that the resultant microcrystalline phase 3 is an achiral complex consisting of one-dimensional coordination chains. Phase 3 undergoes reversible structural transformation via amorphous phase (phase 2) upon dehydration and subsequent rehydration. This amorphous phase shows selective adsorption of water from a water–DMF mixture and water–CCl4 mixture. Phase 1 to phase 3 structural transformation proceeds through selective bond breaking. The magnetic studies of the two crystalline and the amorphous ...

A new metal–organic complex {[Ni(HL1)Cl]2·5H2O} has been synthesized using a Schiff base ligand H2L1 [where H2L1 = N,N′-(2-hydroxy)propylenebis(2-imino-3-oximino)butane] and characterized by single crystal X-ray crystallographic, IR and thermal studies. Structural analysis reveals that the complex crystallizes in achiral C2/c space group and it has 3D supramolecular structure. Hydrogen bonding interactions among the metal–organic moieties form 2D supramolecular sheets within the crystallographic ab-plane. These 2D sheets are packed along crystallographic c-axis with formation of 1D supramolecular channels along crystallographic a-axis and thus the complex behaves like metal–organic supramolecular host (MOSH). Five guest water molecules get stability within the supramolecular channels through hydrogen bonding interactions. Hydrogen bonding interactions among the guest water molecules produce 2D supramolecular sheets within the ab-plane with (H2O)12 morphology. These supramolecular water sheets are of two different types: one contains only right handed helical chains and the other contains only left handed helical chains. The complex undergoes reversible structural transformation upon dehydration–rehydration.

The zinc(II) complex with tridentate thiohydrazone ligand have been prepared by metal template reaction. The metal template reaction was used to prepare the zinc (II) complex with tridentate thiohydrazone ligand. The reaction of diacetylmonoxime and, morpholine N-thiohydrazidewith Zn(OAc)2 $\cdot$ 2H2O under reflux yielded the formation of the [Zn(Hdmmthiol )2] $\cdot$ 2H2O complex. The complex was characterized by a combination of protocols including elemental analysis, UV+vis, FT-IR, TG and PXRD. The temperature dependence of the electrical conductivity and the optical property of the [Zn(Hdmmthiol )2] $\cdot$ 2H2O complex is called H2dammthiol was studied. Powder X-ray diffraction (PXRD) method was used to investigate the crystal structure of the sample. The zinc complex was shown to be a member of the triclinic system. The zinc complex was determined to have n-type conductivity as demonstrated in the hot probe measurements. The complex was determined to display direct optical transition with band gaps of 2.52eV as determined by the optical absorption analysis.

Some Mn(III) complexes of N,N′-(2-hydroxy)propylenebis(acetylacetoneimine) (abbreviated to H2L1) and N,N′-(2-hydroxy)propylenebis(2-imino-3-oximino)butane (abbreviated to H2L2), [Mn(III)(Lig)(X)] (where Lig stands for the dianion of the Schiff-base ligands and X stands for CH3COO−, Cl−, Br−, I−) were synthesized. The complexes are characterized with the help of elemental analyses, magnetic moments, spectroscopic data (UV-Vis, infrared), and molecular weight determination (measured by Rast's method). The structures of the complexes were obtained using density functional theory (DFT). DFT calculation shows that 1–4 and 8 are trigonal-bipyramidal whereas 5–7 are square-pyramidal.

The temperature dependence of electrical conductivity, optical property and crystal structure (PXRD) of [Ni(Hdammthiol)(CH3COO)] (1), [Co(Hdammthiol)(CH3COO)]center dot H2O (2) and [Cu(Hdammthiol)(CH3COO)]center dot H2O (3) [where H(2)dammthiol is the thiol form of the ligand diacetylmonoxime morpholine N-thiohydrazone (Hdammth)] complexes were investigated. The crystal structures of samples at room temperature were examined by using powder X-ray diffraction (PXRD). The results showed that all the complexes belong to the monoclinic system. Hot probe measurement indicated that these complexes had an n-type electrical conductivity. Optical absorption studies in the wavelength range 190-1100 nm at room temperature showed that the optical band gap E-gd of complexes 1-3 is 2.75 eV, 2.37 eV and 1.58 eV, respectively. (C) 2011 Elsevier B.V. All rights reserved.

Two different chiral metal–organic frameworks (CMOF), namely, {[Cu2(1,10-phen)2(tartrate)H2O]·8H2O}n (1) and {[Cu(1,10-phen)(H2tartrate)H2O]·6H2O}n (2) [1,10-phen = 1,10-phenanthroline] have been synthesized with an alteration in the pH of the reaction media. Reflux at 85 °C, complex 1 (pH = 4.95) crystallizes in P21, while simple stirring at room temperature, complex 2 (pH = 4.10) crystallizes in P212121 space group. When the solid-state structure of 1 is compared with complex 2, interesting changes in the supramolecular self-assembly are noticed. CMOF 1 features a 1D supramolecular coordination polymer, in stark contrast, CMOF 2 features 1D coordination polymer. We reveal one helicalassembly in 1 whereas three helicalassembly in 2. The CMOFs exhibit solid-state blue luminescence at room temperature and non-linear optical (NLO) activity.

The condensation of diacetylmonoxime (damnx) with morpholine N-thiohydrazide (mth) in 1:1 molar ratio in ethanol (16 h) afforded a nitrogen–sulfur zwitterionic heterocyclic compound, N-(3,4-dimethyl-1,2,5-thiadiazole-2-ium-2-yl)morpholine-4-carbothioate (dtmc). However, the same reaction in presence of [Zn(OAc)2]·2H2O in ethanol under gentle reflux on (3 h) yielded the zinc complex, [Zn(Hdammthiol)(OAc)(H2O)]·H2O, where H2dammthiol (H2L2) is the thiol form of tridentate NNS donor thiohydrazone ligand, diacetylmonoxime morpholine N-thiohydrazone (Hdammth). Both the nitrogen–sulfur heterocyclic compound and the zinc complex have been characterized by elemental analyses, spectroscopy (IR, UV–Vis, 1H NMR and 13C NMR) and single crystal X-ray crystallography. It is noteworthy that the heterocyclic compound shows S⋯S interaction with distance 2.738 A in its planar conformation. The heterocyclic compound forms two dimensional supramolecular sheets through C–H⋯O and π⋯π interactions while the zinc complex, with distorted square pyramidal geometry, forms 1D supramolecular chain. A mechanism has been proposed for the formation of nitrogen–sulfur heterocyclic compound.

The Reaction of phenylmercury(II) acetate with salicylaldehyde morpholine N-thiohydrazone (H2smth) and 2-hydroxyacetophenone morpholine N-thiohydrazone (H2apmth) in dry ethanol under gentle refluxing condition form light yellow complexes [PhHg(Hsmth)] (1) and [PhHg(Hapmth)] (2) involving formation of Hg-S bond from the thiol form of the ligands after deprotonation of the SH proton. The structures of the complexes as determined by X-ray crystallography shows that the complex (1) has a distorted T-shaped geometry while the complex (2) adopts familiar linear coordination geometry. Complex (2) has two independent molecules comprising the asymmetric unit. Both the complexes form two-dimensional supramolecular assemblies due to a combination of weak intermolecular Hg····π and Hg····Hg interactions. The Hg····π and Hg····Hg distances are 3.937 and 4.0216(10) A, respectively, possibly indicating weak mercuriophilic interactions. The luminescent properties of the complexes in solution and in the solid state at room temperature are also described.

Reactions of 2-(L-carboxyl-2-hydroxyphenyl)thiazolidine with different chromium(III) salts [CrCl3 · 6H2O, K3[Cr(SCN)6], NH4[Cr(NH3)2(SCN)4] · H2O, [Cr(urea)6]Cl3 · 3H2O and [Cr(CH3COO)2H2O]2] under varied reaction conditions afforded many new mixed-ligand chromium(III) complexes. The ligand is a tridentate dibasic NSO donor except for complexes 1 and 4 where two moles of the ligand are present for each molecule of complex, one functioning as a dibasic tridentate (NSO) and the other as a monobasic bidentate (NS) (phenolic OH and carboxylic COOH groups remaining uncoordinated). The complexes have been characterized by elemental analyses, magnetic susceptibilities, molar conductances, molecular weights and spectroscopic (IR, Uv-vis) data. The ligand field parameters and NSH Hamiltonian parameters suggest tetragonal geometries of the complexes.

The reaction of phenylmercury(II) acetate and cadmium(II) acetate with a refluxed solution of diacetylmonoxime and morpholine N-thiohydrazide formed a novel phenylmercury(II) complex, [PhHg(Hdammthiol)] (1) and a cadmium(II) complex, [Cd(Hdammthiol)2] (2), respectively (where H2dammthiol is the thiol form of diacetylmonoximemorpholine N-thiohydrazone (Hdammth) formed by the condensation of diacetylmonoxime and morpholine N-thiohydrazide in the presence of phenylmercury(II) and cadmium(II) ions). The complexes were characterised by elemental analyses and spectral data (electronic, infrared and 1H NMR) and also by X-ray crystal structure analysis. The X-ray crystallography shows that the phenylmercury(II) complex attained a tricoordinated distorted T-shaped structure, while the cadmium(II) complex attained a trapezoidal bipyramidal geometry. The phenylmercury(II) complex forms a two-dimensional sheet via C–H⋯O and O–H⋯N hydrogen bonding and also forms a two-dimensional supramolecular dimer, having C–H⋯π synthons. Intermolecular C–H⋯O and O–H⋯O hydrogen bonding of the cadmium(II) complex forms a two-dimensional supramolecular sheet along the bc plane and posses an impressively short intermolecular C(sp3)⋯O(sp3) contact.

Condensation of 1,3-diaminopropane-2-ol with diacetylmonoxime, acetylacetone, salicylaldehyde and orthohydroxyacetophenone yielded the tetradentate Schiff bases N,N′-(2-hydroxy)propylenebis{(2-imino-3-oximino)butane} (H2dampnol), N,N′-(2-hydroxy)propylenebis(acetylacetoneimine) (H2acacpnol), N,N′-(2-hydroxy)propylenebis-(salicyalaldimine) (H2salpnol) and N,N′-(2-hydroxy)propylenebis(7-methylsalicylaldimine) (H2ohacpnol), respectively. The ligands form complexes with oxovanadium(IV), vanadium(IV) and oxovanadium(V) salts. Some mixed ligand complexes involving σ-bonded phenyl and benzyl radical along with tetradentate ligand, H2L (where, H2L stands for H2dampnol, H2acacpnol, H2salpnol or H2ohacpnol) of the types [(L)V(C6H5)2]CH3OH and [(L)V(CH2Ph)2]CH3OH have been synthesized, characterized and also provide the syntheses of some new organovanadium(IV) complexes. Silylation coupled with desilylation have been employed as a route to new organovanadium(IV) complexes. All the complexes have been characterized w...

The reaction of 3-formylsalicylic acid with morpholine N-thiohydrazide produces 3-carboxy-2-hydroxybenzaldehyde morpholine N-thiohydrazone (H2chbmth) which remains in equilibrium in solution with its corresponding thiol form H3chbmthol having an NSO donor set of atoms. The reactions of the thiohydrazone ligand with different organometallic compounds viz. R2MCl2 (R = π-C5H5 & M = Ti/Zr; R = Me/Ph & M = Sn; R = OMe & M = Sn), (π-C5H5)2Ti(OMe)Cl2 and RMCl3 (R = Me/Ph & M = Sn; R = π-C5H5 & M = Ti) leading to the syntheses of many new organometallic derivatives have been studied. In all of the complexes the dianion of the H3chbmthol ligand functions as a dibasic tridentate NSO donor. The reactions of [(π-C5H5)Ti(Hchbmthol)Cl] and [MeSn(Hchbmthol)Cl], isolated in this study, with Me3SiE (where, E stands for NMe2 and C≡CPh) and MeSH have also been studied and many new organoderivatives of these two metal ions isolated. All the compounds under study have been characterized by elemental analyses, magnetic suscept...

The reaction of [Cr(urea)(6)]Cl(3).3H(2)O with H(2)salen (H(2)salen=N,N(')-ethylenebis(salicylaldimine) in water-methanol mixture (40:60v/v) under reflux yielded the complex bis[N-(2-aminoethyl)salicylaldiminato]chromium(III) chloride monohydrate, [Cr(aesaldmn)(2)]Cl.H(2)O. The complex was characterized by elemental analysis, molar conductance, magnetic susceptibility, spectroscopic (UV-vis and IR) data and X-ray diffraction studies. The new ligand, N-(2-aminoethyl)salicylaldimine, Haesaldmn, possibly resulted from the hydrolytic cleavage of one end of the H(2)salen ligand during reflux. Binding of this chromium(III) complex to CT DNA has been studied using UV-vis spectroscopy with an apparent binding constant of 2.68 x 10(3)M(-1). It shows that the binding mode is electrostatic while the emission of ethidium bromide to CT DNA in the absence and in the presence of the complex show that it binds DNA with partial intercalation.

A new octahedral chromium(III) complex having 2,2'-bipyridine as ligand system was synthesized in methanol. Single crystal X-ray diffraction analysis shows that it possesses non-stoichiometry in its anionic primary covalency. It has also been studied by elemental analyses, optical spectroscopy (UV-vis, IR) and magnetic susceptibility data. DFT calculations (with B3LYP functional and double-xi quality LANLDZ(D95V) basis set) were carried out to interpret the electronic and infrared spectra of the complex. The DFT optimized geometric structure for the complex is compared with the X-ray crystallographic data; the theory-experiment agreement is satisfactory.

The reaction of 3-formylsalicylic acid with morpholine N-thiohydrazide in ethanol leading to the formation of a new thiohydrazone, 3-carboxy-2-hydroxybenzaldehydemorpholine N-thiohydrazone (H2chbmth) is described. This thiohydrazone ligand remained as the thio-keto form in the solid state. However, thioketo- and a small amount of the thiol-tautomeric forms (H2chbmth and H3chbmthol, respectively) remain in equilibrium in solution. The reactions of the ligand with different metal salts (in 1 : 1 molar ratio) leading to the synthesis of many new metal complexes have been studied. Depending on pH of the reaction medium and the nature of the metal salt used, the ligand is found to be monobasic tridentate, dibasic tridentate, monobasic bidentate or neutral bidentate giving complexes [Co(H2chbmth)2]X2, [X = NO3 (11), ½SO4 (13)]; [Cd(H2chbmth)(H2O)2]SO4 (21); [M(Hchbmth)X], [M = Cu(II) and X = Cl (1), NO3 (2), CH3COO (4); M = Ni(II) and X = Cl (6), NO3 (7); M = Co(II) and X = NO3 (12), CH3COO (14); M = Zn and X =...

The reaction of 3-formylsalicylic acid with 2-aminoethanethiol produces 2-(1-carboxyl-2-hydroxyphenyl)thiazolidine (H2chptz) which remains in equilibrium in solution with its corresponding Schiff base, 3-carboxysalicylidenethioethanolimine (H3mcsalim) having an NSO-donor set of atoms. The reactions of the thiazolidine ligand with different metal salts leading to the synthesis of many new metal complexes and organometallic derivatives have been studied. For all the complexes the dianion of the Schiff base, H3mcsalim acts as a tridentate NSO donor ligand. The reactions of [(Hmcsalim)Ti(π-C5H5)Cl] and [(Hmcsalim)Sn(Me)Cl], isolated in this study, with Me3SiE (where, E stands for SMe, NMe2 and C≡CPh) have also been studied. The elemental analyses, magnetic susceptibilities, molar conductance values, EPR-study, CV, molecular weights and spectroscopic (UV-Vis, IR, 1H NMR) data characterize all the compounds under study. Based upon these data the geometry of the compounds has also been proposed.

Reaction of 3‐formylsalicylic acid with diethylenetriamine yielded the Schiff base {N,N′–2,2′‐bis(aminoethyl)methylaminebis(3‐carboxysalicylaldimine)}, abbreviated as H4fsadien. The interaction of H4fsadien with CoCl2 · 6H2O, Ni(OAc)2 · 4H2O, Cu(OAc)2 · H2O, Zn(OAc)2 · 2H2O, Na2MoO4 · 2H2O, WO2(acac)2, (NH4)2[MoOCl5], (pyH)2[Mo(SCN)6], FeSO4 · 7H2O and FeCl3 · 6H2O under varied reaction conditions have been studied. The reactions of some of the new metal complexes isolated in this study have also been investigated with a view to develop new preparative methods. The Schiff base H4fsadien was found to act as a dibasic tetradentate ligand or as a dibasic pentadentate ligand, by using N2O2 or N3O2 donor sites, respectively. Elemental analyses, molecular weights, magnetic moment values, molar conductances and spectroscopic (IR, UV‐Vis and 1H NMR) data characterize the complexes. The authors are thankful to the Regional Sophisticated Instrumentation Centre, the Central Drug Research Institute, Lucknow, for elem...

Condensation of 1,3‐diaminopropane‐2‐ol with diacetylmonoxime and acetylacetone yielded the tetradentate Schiff bases N,N′‐(2‐hydroxy)propylene‐bis{(2‐imino‐3‐oximino)butane} (H2L1) and N,N′‐(2‐hydroxy)propylene‐bis(acetylacetoneimine) (H2L2), respectively. The ligands form mononuclear manganese(II) complexes of the type [Mn(II)(L1)] (1) and [Mn(II)(L2)] (3), which are used for the formation of the manganese(III) heterochelates of the type [Mn(III)(L)(L‐L)] (where H2L = H2L1 or H2L2; L‐L = anion of acetylacetone or salicylaldehyde). Cationic heterochelates of the type [Mn(L)(L‐L)]ClO4 where H2L = H2L1 or H2L2 and L‐L = ethylenediamine and N,N′‐propylene‐bis(benzaldimine) (L3) have been synthesized by the reactions of bis(acetylacetonato)manganese(II) or bis(salicylaldehydato)manganese(II) with the preformed Schiff bases or by the reactions of [Mn(II)(L1)] or [Mn(II)(L2)] with L‐L in absolute alcohol under reflux. Some of the complexes, synthesized here, may be used as precursors in the synthesis ...

Herein, we report the structural, optical, thermal and electrical transport properties of a new multicomponent salt (TBTA2−)·2(IM+)·(water) [TBTA–IM] of tetrabromoterepthalic acid (TBTA) with imidazole (IM). The crystal structure of TBTA–IM is determined by both the single crystal and powder X-ray diffraction techniques. The structural analysis has revealed that the supramolecular charge assisted O−⋯H N+ hydrogen bonding and Br⋯π interactions play the most vital role in formation of this multicomponent supramolecular assembly. The Hirshfeld surface analysis has been carried out to investigate supramolecular interactions and associated 2D fingerprint plots reveal the relative contribution of these interactions in the crystal structure quantitatively. According to theoretical analysis the HOMO–LUMO energy gap of the salt is 2.92 eV. The salt has been characterized by IR, UV–vis and photoluminescence spectroscopic studies. It shows direct optical transition with band gaps of 4.1 eV, which indicates that the salt is insulating in nature. The photoluminescence spectrum of the salt is significantly different from that of TBTA. Further, a comparative study on the antibacterial activity of the salt with respect to imidazole, Gatifloxacin and Ciprofloxacin has been performed. Moreover, the current–voltage (I–V) characteristic of ITO/TBTA–IM/Al sandwich structure exhibits good rectifying property and the electron tunneling process governs the electrical transport mechanism of the device.

To explore the influence of non-covalent weak force interactions, mainly exerted by carboxylic groups, on the formation of supramolecular architectures of transition metal complexes and their electrical conduction processes, a new symmetrical [N4O2] hexadentate Schiff base ligand, 1,8-N-bis(3-carboxy)disalicylidene-3,6-diazaoctane-1,8-diamine, abbreviated to H(4)fsatrien, and its complexes of Ni(II), Cd(II) and Mn(II) have been synthesized using in situ condensation of the ligand components in the presence of metal ions. The complexes were structurally characterized by elemental analyses, IR, UV-Vis, NMR. ESR, molar conductivity and magnetic measurements. The crystal structures of all the complexes have been determined by a single crystal X-ray diffraction study. The 1-D, 2-D and 3-D networks of the complexes are formed by pi-pi stacking, C-H...pi interactions and mono or bifurcated H-bonding. The electronic structures of the complexes have been examined using the DFT method. Solid-state properties (e.g. electrical conductivity at different temperatures and optical properties) of the Ni(II) and Mn(II) complexes have also been studied and, depending on the temperature, the conductivity of the complexes is found to be insulating and semiconducting (intrinsic and extrinsic) in nature. The optical band gap (E-gd) of complexes (1) and (3) is found to be 2.57 and 2.30 eV, respectively. (C) 2008 Elsevier Ltd. All rights reserved.

Four homodinuclear complexes of Ni(II)–Ni(II), Cu(II)–Cu(II), Co(II)–Co(II) and Co(III)–Co(II) and five heterodinuclear complexes of Co(III)–Zn(II), Co(III)–Cu(II), Co(III)–Ni(II), Cu(II)–Zn(II) and Zn(II)–Cu(II) with the octadentate Schiff base compartmental ligand 1,8- N -bis(3-carboxy)disalicylidene-3,6-diazaoctane-1,8-diamine (H 4 fsatrien) have been synthesized. The complexes have been characterized with the help of elemental analyses, molecular weights, molar conductances, magnetic susceptibilities and spectroscopic (UV–vis, IR, ESR) data. Cryomagnetic data also helped to elucidate the structural features of the Cu(II) complexes.

The metal complexes, [M(Hdammthiol)(2)]Cl·3H(2)O [M = Cr(III) (1), Fe(III) (2)] [where H(2)dammthiol is the thiol form of the ligand, diacetylmonoxime morpholine N-thiohydrazone] were synthesized by metal template reactions of diacetylemonoxime with morpholine N-thiohydrazide in the presence of CrCl(3)·6H(2)O and FeCl(3)·6H(2)O. Both the complexes (1 and 2) were characterized by single crystal X-ray crystallography, spectroscopic (IR and UV-vis), Mössbauer and TGA analyses. The single crystal X-ray studies of both complexes show that the supramolecular hosts, constructed by the discrete mononuclear complexes, form supramolecular channels along the c-axis which are filled up by water-chloride clusters. In both complexes, the 1D water-chloride chain with chair-like architecture within the supramolecular hosts presents novelty. The magnetic measurement study of Fe(III) complex shows a spin crossover from S = 1/2 at 2.5 K to S = 5/2 at 300 K. At very low temperature, the presence of strong cooperative hydrogen bonding interactions stabilizes the S = 1/2 state.