Search

The novel mononuclear Cd(II) metalloreceptor Cd[LH2I2] (complex 1), derived by the reaction of the Schiff base ligand 6,6′-(1E,1′E)(ethane-1,2 diylbis(azaneylidene))bis(methaneylylidene)bis(2-ethoxyphenol) (H2L) and CdI2, was successfully used to detect Zn(II) and Mg(II) in semi-aqueous and aqueous media, respectively, among several competitive cations. The single crystal data analysis revealed that the asymmetric unit of complex 1 consists of one ligand, H2L, and two I-ions, compensating the +2 oxidation state of Cd. The optically monitored sensing of Zn(II) and Mg(II) by complex 1 was further assessed by utilizing UV and fluorescence spectroscopic techniques. The remarkable enhancement of the fluorescence intensity of complex 1-Zn(II) and complex 1-Mg(II) in the presence of CH3COO− and SO4= indicated that a heteronuclear bridging complex could be obtained if two separate reactions of complex 1 with (CH3COO)2Zn and MgSO4 could be carried out. Interestingly, two different single crystals of Cd–Zn (complex 2) and Cd–Mg (complex 3) were obtained after conducting two separate reactions of complex 1 with Zn(II) and Mg(II). Single crystal data analysis showed that complex 2 is an octanuclear Zn(II)/Cd(II) complex with the presence of acetate and an hydroxy group, and both metal centers are in the +2 oxidation state. The IR and NMR spectra results confirmed the formation of complexes 2 and 3. The SPX and EDX studies confirmed the presence of Zn(II) and Mg(II) in complex 2 and complex 3, respectively. The limit of detection for sensing of both was measured in the nanomolar range. Although it is well-known that mononuclear Cd complexes are effective Schottky devices, there have been few reports of investigation of heteronuclear Cd(II) complexes as candidates for effective Schottky devices, or determination of the values of device performance, conductivity, and device parameters with heteronuclear Cd complexes 2 and 3. Surprisingly, all the results indicated that a potential Schottky device could be produced due to the efficacy of complex 2 with respect to complex 3. The effectiveness of the device would be satisfactory because of the lower band gap value and the presence of weak intramolecular π–π stacking interactions in complex 2. [ABSTRACT FROM AUTHOR]

Three mixed-valence trinuclear cobalt(III)–cobalt(II)–cobalt(III) complexes, [CoII{(μ-L1)(μ-OAc)CoIII(OAc)}2]·2.67H2O (1), [CoII{(μ-L1)(μ-OOCPh)CoIII(DMSO)0.8(OOCPh)0.2}2](ClO4)1.6 (2) and [CoII{(μ-L2)(μ-OOCPh)CoIII(DMSO)0.75(OOCPh)0.25}2](ClO4)1.5 (3), have been synthesized using two tetradentate N2O2 donor 'reduced Schiff base' ligands, H2L1 {1,3-bis(2-hydroxybenzylamino)2,2-dimethylpropane} and H2L2 {2,2′-[1,1′-(propane-2,2-diyldiimino)diethylidene]diphenol}, and acetate or benzoate as anionic co-ligands. These complexes have been characterized by spectroscopic measurements and their solid state structures have been determined by single crystal X-ray diffraction analysis. The cobalt(III)–cobalt(II)–cobalt(III) skeletons of complexes 1 and 2 are linear, centrosymmetric; but in complex 3, it is non-centrosymmetric. Both the central cobalt(II) and terminal cobalt(III) atoms are hexa-coordinated in all three complexes. The structure directing role of several noncovalent interactions in the solid state of the complexes has been investigated focusing on the H-bonding interactions mediated by the co-crystallized water molecules in 1 and the perchlorate counterions in 2 and 3. Thermo-gravimetric analysis (TGA) provided a thermal driven pathway to observe the loss of lattice water molecules from complex 1. All the complexes show good electrical conductivity, which has been rationalized by band gap measurements. The band gap in the solid state was determined experimentally and also by DFT calculations and it confirms that each of the complexes behaves as a semiconductor. These complexes have been used to fabricate Schottky barrier diodes. [ABSTRACT FROM AUTHOR]

Different aliphatic amine (including triethylamine (TEA), ethylenediamine (EN), N,N,N0, N0-tetramethylethylenediamine (TEMED), diethylenetriamine (DETA), triethylenetetramine (TETA)) directed Mg(II)-metallogels have been successfully achieved. Amines with single or multiple N-site(s) are utilized for the origination of stable Mg(II)-metallogels. Exhaustive rheological investigations establish the mechanical stability of the Mg(II)- metallogels. The thixotropic properties of the rheological experiments clarify the self-healing nature of different Mg(II)-metallogels. The morphological variations of different aliphatic-amine-directed metallogels are verified through scanning electronic microscopic images. The presence of metallogel-forming chemicals has been experimentally checked through elemental analyses. The electrical properties of the self-healable Mg(II)- metallogel-based systems have been explored. The I-V characteristics of different metallogels show a Schottky device nature for a gel-directed sandwich configuration with an ITO/metallogels/Al structure. The metallogelmediated fabricated metal-semiconductor junction devices show very prominent rectification ratios (on-off ratio). [ABSTRACT FROM AUTHOR]

A new mononuclear Fe3+ metalloligand MC1 [FeLN3(H2O)], developed by using the N2O2 donor Schiff base ligand H2L, has been successfully used to detect and remove Hg2+ and Cd2+ from several transition metal ions with the formation of two unusual hetero metallic μ-oxo Fe3+–Hg2+/Cd2+ clusters, [(Fe23+)(μ-O)L2Cl4(Hg22+)] (MC2) and [(Fe23+)(μ-O)L2I4Cd22+] (MC3) [(where H2L is 6, 6′-(1E, 1′E) (ethane-1, 2 diylbis(azaneylidene))bis(methaneylylidene))bis(2-ethoxyphenol)]. All three complexes were identified by X-ray single-crystal data analysis along with a range of spectral studies. In MC1, the Fe3+ is coordinated with deprotonated H2L, one water molecule, and one azide ion as a secondary anionic residue, forming an octahedral geometry. Interestingly, MC2 and MC3 are isostructural, where each asymmetric unit contains deprotonated H2L, one Fe3+ and Hg2+/Cd2+ metal center, two Cl−/I− and two Fe3+ centers are connected by a μ-O bridge to form tetranuclear complexes. As the band gap energy values of MC1, MC2, and MC3 (3.07 eV, 2.69 eV, and 2.55 eV, respectively) are in the visible region so all the three complexes are exposed to investigate their potentiality to be effective Schottky devices and at the same time a thorough inspection has been carried out to check their catalytic behaviour in aqueous medium in terms of methylene blue (MEB) dye degradation under visible light irradiation. A thorough inspection reveals the better MB dye degradation potentiality of MC3 in comparison to MC2 in the presence of H2O2. At the same time, the investigation of the device performances, conductivity, and device parameters disclose more effectiveness of MC3 in comparison to MC2 in a better Schottky device. The effectiveness of MC3 in both applications may be attributed to its lower band gap value. [ABSTRACT FROM AUTHOR]

Herein, we have presented the crystal structure, supramolecular structure and band structure along with dielectric, electrical transport and optoelectronic properties of a [Mg(H2O)6]2+ templated 3D hydrogen bonded supramolecular framework (HSF) {[Co(2,5-Pdc)2,(H2O)2]2−·[Mg(H2O)6]2+·4(H2O)} (where 2,5-pdc = 2,5-pyridinedicarboxylate) synthesized by reflux method. The complex crystallizes in the P1¯ space group. The 3D network of the complex has been built up by hydrogen bonding interactions between 2D supramolecular sheets of the complex. The proton conductivity and activation energy of the complex are ∼10−4 S cm−1 at 40 °C and ∼0.3 eV, respectively, under vacuum. It exhibits anomalous dielectric behavior due to the gradual release of guest water molecules above 40 °C. The complex is a semiconductor with a band gap of 1.626 eV and is capable of absorbing electromagnetic radiation in the range of 355–730 nm. The ITO/complex/Al sandwiched device exhibits Schottky barrier diode (SBD)-like behaviour with a rectification ratio of 13 in the dark and 34 under visible light at 1 V. When exposed to visible light (AM 1.5G) the value of its conductivity enhances 1.35 times, compared to that in the dark. It has been shown that the complex is a semiconducting proton conducting photoresponsive HSF. [ABSTRACT FROM AUTHOR]

An intriguing rapid self-healing functional Mg(OH)2 metallogel was instantaneously developed through the direct mixing of monoethanolamine and magnesium nitrate hexahydrate as the source of magnesium ions in a water medium at room temperature under atmospheric pressure. The rheological properties of the Mg(OH)2 metallogel were scrutinized, and this revealed the mechanical toughness of the semi-solid metallogel material. The outcome of the rheological experiment showed the self-healing property of the metallogel. The self-healing feature was rapid and it occurred within a few minutes of the insertion of a crack into the metallogel or the association of two separate metallogel parts. The morphology of the metallogel was visualized through field emission scanning electron microscopy and EDX spectral investigations. The experimentally estimated optical band gap suggested the semiconducting nature of the material. The semiconducting nature of the metallogel was further verified from the electrical properties. Finally, a technologically challenging device-type application was also realized by the successful fabrication of a Schottky barrier diode, and different device parameters were investigated to verify the performance. The fabricated diode based on the Mg(II) metallogel showed a very high ON/OFF ratio of 85.52. [ABSTRACT FROM AUTHOR]

(E)-N′-((7-Hydroxy-4-methyl-2-oxo-2H-chromen-8-yl)methylene)picolinohydrazide (H-CPh), a greenish yellow emitter in the solid state, aggregates in DMSO solution upon increasing the percentage of water (>50%) and the maximized emission intensity was reached at 90% water–DMSO medium. Upon excitation at 400 nm in pure aquatic medium (HEPES buffer, pH 7.2) H-CPh shows fluorescence sensitivity to Al3+ (λem, 470 nm) and forms a 1 : 1 complex, [(CPh)Al(OH)(H2O)]NO3, with a limit of detection (LOD) of 6.99 nM. The complex, [(CPh)Al(OH)(H2O)]NO3 shows sensitivity to nitroaromatics by quenching the strong emission of the fluorogenic complex and the LODs are: 2,4-dinitrophenol (DNP), 1.67 μM and 2,4,6-trinitrophenol (TNP) 0.99 μM. The H-CPh is electronically a semiconductor and the experimental (2.78 eV) and the DFT derived (2.75 eV) band gaps are comparable. The H-CPh forms a Schottky diode and its photoconductivity (19.98 × 10−4 S m−1) is three times higher than the dark phase conductivity (6.42 × 10−4 S m−1). [ABSTRACT FROM AUTHOR]