Reena Yadav

Luminescent sensing from a new Zn(II) metal–organic framework

A new metal–organic framework having the formula (NH2(CH3)2)[Zn2(OAc)(L)]·0.5DMF (H4L = 2,5-di(3′,5′-dicarboxylphenyl)pyridine) (GDMU-3) has been synthesized and characterized. The net of GDMU-3 is uninodal and is closely related to the lvt net, which has the same Schlafli symbol of 42·84. GDMU-3 displays selective properties for the detection of nitrobenzene and Fe3+ ions. Remarkably, GDMU-3 exhibits an excellent capability to adsorb methylene blue with high selectivity. The present work indicates that GDMU-3 could be a potential candidate for developing novel luminescence sensors for the selective sensing of nitrobenzene which can be deployed for explosives, Fe3+ and organic dyes.

Fluorescence sensing of nitro-aromatics by Zn(II) and Cd(II) based coordination polymers having the 5-[bis(4-carboxybenzyl)-amino]isophthalic acid ligand

Three new coordination polymers (CPs) viz. [Zn2(L)]n (1), {[Cd3(L)2(H2O)][Na2(μ2-H2O)(H2O)7]}n (2) and [Zn2(L)(phen)2(H2O)·H2O]n (3) were synthesized by the reaction between 5-[bis(3-carboxybenzyl)-amino]isophthalic acid (H4L) Zn(NO3)2 (1)/Cd(NO3)2 (2) or Zn(NO3)2 and H4L in the presence of 1,10-phenanthroline (phen) (3) and characterized. X-ray single-crystal analyses reveal that 1 possesses a 3D architecture with a {4·62}{4·82}{42·65·88} topology, whereas 2 shows a unique (4,8)-connected 3D framework with a {411·615·82}{45·6}{46} topology. In the case of 3, the L and phen ligands linked the Zn(II) atoms into a deeply corrugated 2D sheet. The results showed that the structural diversity of the polymers resulted from the different geometries of the metal ions and the effect of the assistant ligands. The photoluminescence sensing of nitro-aromatics by 1–3 indicates that these CPs could be prospective candidates for developing luminescence sensors for selective sensing of these species. Theoretical and experimental investigations indicate that the observed quenching in the photoluminescence intensities of 1–3 by nitro-aromatics may be assigned to the occurrence of both electron and energy transfer processes, in addition to electrostatic interaction between the CPs and nitro-aromatics.

Synthesis, characterization and light harvesting properties of Sb(III) and Bi(III) ferrocenyl dithiocarbamate complexes

New Sb(III) and Bi(III) ferrocenyl dithiocarbamate complexes viz. [Sb(FcCH2Bzdtc)3] (Sb) and [Bi(FcCH2Bzdtc)3] (Bi) (Fc=C5H5FeC5H4-; Bz=C6H5CH2-) have been synthesized and characterized by elemental analyses, IR, (1)H and (13)C NMR spectroscopies. The optical, electrochemical and photovoltaic properties of the synthesized complexes were investigated. The light harvesting properties of both of the compounds have been studied using these compounds as photosensitizers in TiO2-based DSSCs. The photovoltaic devices fabricated by Sb and Bi showed a maximum current conversion efficiency of 1.51% and 0.97%, respectively under 1.5 AM illumination (100 mW cm(-2)) and having incident photon to current efficiency (IPCE) of 38% and 31%, respectively. The reason for the higher efficiency of Sb is due its higher dye loading.

New Ni(II) 1,2-bis(diphenylphosphino)ethane dithiolates: crystallographic, computational and Hirshfeld surface analyses

Three new nickel(II) 1,2-bis(diphenylphosphino)ethane dithiolate complexes viz. [Ni(dppe)(benzylcyanidedithiolate)] (1), [Ni(dppe)(2-cyanobenzylcyanidedithiolate)] (2) and [Ni(dppe)(pyridine-2-cyanidedithiolate)] (3) have been synthesized and characterized spectroscopically and by single-crystal X-ray analysis. The X-ray analyses of 2 and 3 reveal a distorted square planar geometry around Ni(II) satisfied by the two sulfur atoms of the dithiolate and two phosphorus atoms of the dppe ligands. Both 2 and 3 display intermolecular C–N⋯H, π⋯π and C–H⋯π and C–S⋯H interactions which generate a supramolecular framework. Additionally, both 2 and 3 show intramolecular C–H⋯Ni anagostic interactions. These interactions have been addressed by ab initio, AIM and Hirshfeld surface analyses. The anagostic interactions are verified using bond order and natural charge calculations which indicated depletion of electron density on the ortho-hydrogen atoms undergoing the anagostic interactions. All three compounds exhibit photoluminescence in dichloromethane solution as well as in the solid state. The solid-state emissions are red-shifted in comparison to the solution-phase emissions which may be attributed to the existence of intermolecular interactions in the solid state.

Ferrocenyl chalcones with phenolic and pyridyl anchors as potential sensitizers in dye-sensitized solar cells

Five ferrocenyl chalcones viz. (E)-1-(3′-hydroxyphenyl)-3-ferrocenylprop-2-en-1-one (H-1), (E)-1-(4′-hydroxyphenyl)-3-ferrocenylprop-2-en-1-one (H-2), (E)-1-(2′-hydroxyphenyl)-3-ferrocenylprop-2-en-1-one (H-3), (E)-1-(4-pyridyl)-3-ferrocenylprop-2-en-1-one (H-4) and (E)-1-(2-pyridyl)-3-ferrocenylprop-2-en-1-one (H-5) having hydroxyl or pyridyl as the anchoring group have been synthesized and characterized using microanalyses, IR, 1H and 13C NMR, and in three cases, using single-crystal X-ray diffraction. UV-vis spectroscopic studies indicates that in comparison to ferrocene the electronic absorption bands of the synthesized dyes H-1–H-5 are bathochromically shifted up to 530 nm with concomitant enhancement in their intensities. The synthesized dyes have been exploited as photosensitizers in TiO2-based dye-sensitized solar cells (DSSCs). The photovoltaic performances and charge transport properties (EIS spectra) were studied to evaluate the synthesized dye performances in DSSCs. Amongst all the ferrocenyl chalcone dyes, those with the hydroxyl linker H-1–H-3 showed relatively superior photovoltaic performance in comparison to the dyes having a pyridyl anchor. The superior performances of H-1–H-3 are probably due to the better electronic communication between the ferrocene and the six-membered aromatic ring with anchoring group as well as the high dye loading abilities of these compounds on the TiO2 surface, which suppress charge recombination, prolong electron lifetime, and decreases the total resistance of DSSCs. The assembly fabricated using H-2 showed the best performance with an overall conversion efficiency η of 6.55%, Jsc of 11.99 mA cm−2 and Voc of −0.74 V. The long term stability of the photocurrent output of the cell using H-2 as photosensitizer has been monitored during 700 h which shows 92% retention of the cell parameters. Also, H-2 showed better thermal stability than the state-of-the-art N719 dye and also has a comparable lifetime of electrons in the conduction band.

1,2-Bis(diphenylphosphino)ethane nickel(ii) O,O'-dialkyldithiophosphates as potential precursors for nickel sulfides

In this work, three heteroleptic Ni(II)dppe dithiophosphate complexes, [Ni{S2P(OC2H5)2}(dppe)]B(C6H5)4 (1), [Ni{S2P(OCH(CH3)2)2}(dppe)]PF6 (2) and [Ni{S2P(OCH(CH3)2)2}(dppe)]B(C6H5)4 (3) (dppe=1,2-bis(diphenylphosphino)ethane), have been synthesized and characterized by analytical and spectroscopic techniques (microanalysis, IR, UV-Vis, 1H, 13C and 31P NMR spectroscopy) as well as single crystal X-ray crystallography. The crystal structures of all complexes displayed a distorted square planar geometry around the Ni(II) center bonded through two sulfur atoms of the dithiophosphate ligand and two phosphorus atoms of dppe. The TGA results indicated that all three compounds display loss of solvents at the outset and decompose to Ni–S phase systems and hence may act as potential precursors for nickel sulfides. Investigations indicated that the bulkiness of counteranions as well as the alkyl fragment of the dithiophosphate ligands do not have any effect on the morphologies of as-synthesized nickel sulfides.

Ferrocenyl benzimidazole with carboxylic and nitro anchors as potential sensitizers in dye-sensitized solar cells

Two ferrocenyl benzimidazoles with carboxylic (1) and nitro (2) anchors have been synthesized and characterized using microanalyses, IR, 1H and 13C NMR spectroscopy, and in one case using single crystal X-ray diffraction. UV-Vis spectroscopic studies indicate that in comparison to ferrocene the electronic absorption bands of the synthesized 1 and 2 dyes are bathochromically shifted up to 530 nm with concomitant enhancement in their intensities. The synthesized dyes have been exploited as a photosensitizer in TiO2-based dye-sensitized solar cells (DSSCs). The photovoltaic performances and charge transport properties (EIS spectra) were studied to evaluate the synthesized dye performance in DSSCs. Amongst both the dyes, the one with the carboxylic anchor showed relatively superior photovoltaic performance in comparison to the dye with a nitro anchor. The superior performance of 1 is probably due to the better anchorage and superior dye loading capability on the TiO2 surface, which suppresses charge recombination, prolongs electron lifetime, and decreases the total resistance of the DSSC. The assembly fabricated using 1 showed the best performance with an overall conversion efficiency η of 5.81%, Jsc of 12.74 mA cm−2, and Voc of −0.648 V. The obtained efficiency is ∼84% of the cell efficiency compared with the state-of-the-art N719 dye in similar conditions.

Microwave directed metal-free regiodivergent synthesis of 1,2-teraryls and study of supramolecular interactions

A microwave directed, simple and efficient synthesis of 3′-amino-5′-(sec.amino)-[1,1′:2′,1′′-teraryl]-4′-carbonitriles has been delineated through ring transformation reaction of 6-aryl-2-oxo-4-sec.amino-2H-pyran-3-carbonitriles by benzyl cyanide under basic conditions. Reaction of 6-aryl-4-sec.amino-2-oxo-2H-pyran-3-carbonitriles and benzyl cyanide in DMSO and KOH as a base at 15 °C provides (2E,4E)-5-aryl-6-oxo-6-phenyl-3-sec.amino-hexa-2,4-dienenitriles. Reaction of 6-phenyl-4-(piperidin-1-yl)-2-oxo-2H-pyran-3-carbonitrile and benzyl cyanide in DMF and sodamide at 100 °C provides 1,5-diphenyl-3-(piperidin-1-yl)cyclopenta-2,4-diene-1,2-dicarbonitrile. Use of microwave irradiation diverts the regioselectivity and changes the course of reaction and 1,2-teraryls was isolated. The structure of one of the compound was confirmed by single crystal X-ray and the nature of weak interactions in the compound has been addressed using ab initio, atoms in molecules (AIM) and Hirshfeld surface analysis.