Biswajit Bhattacharya

Cd(II) based metal–organic framework behaving as a Schottky barrier diode

A metal-organic framework (MOF) of cadmium(ii) is reported here which is the first example of an experimentally achieved MOF based electronic device, and in the present case it is a Schottky diode.

Selective carbon dioxide adsorption by mixed-ligand porous coordination polymers

Porous coordination polymers (PCPs), also referred to as metal–organic frameworks (MOFs), have firmly established themselves as a class of excellent solid-state sorbents for carbon dioxide (CO2) along with their other several exciting properties. The mixed-ligand PCPs, constructed with polycarboxylates and N,N′-donor ligands, have been adopted for the fabrication of novel functional PCPs/MOFs, as the combination of different ligands with metal ions offer a better control over the structural variation of the frameworks compared to a single ligand. In this highlight, we have emphasized some of such important mixed linker-based MOFs with different carboxylate ligands and N,N′-donor linkers that act as excellent materials for CO2 adsorption and separation. The prospect of such mixed-ligand MOFs for the effective separation and sequestration of CO2 is also addressed by means of discussing different strategies for designing mixed-ligand MOFs that not only can potentially improve the amount of CO2 adsorption but also can increase the selectivity of CO2 uptake over other gases and volatiles.

Five diverse bivalent metal coordination polymers based on benzene dicarboxylate and bent dipyridyl ligands: syntheses, structures, and photoluminescent properties

Five new mixed ligand coordination polymers, {[Co0.5(H2O)(1,4-bdc)(3-bpdb)Co0.5(H2O)2]·(H2O)3}n (1), [Co(3-bpdh)(1,4-bdc)(H2O)2]n (2), [Zn(3-bpdb)(1,4-bdc)]n (3), {[Zn(3-bpdh)(1,4-bdc)]·(3-bpdh)0.5}n (4) and [Cd(3-bpdb)(1,4-bdc)(H2O)]n (5) [where 3-bpdb = 1,4-bis-(3-pyridyl)-2,3-diaza-1,3-butadiene; 3-bpdh = 2,5-bis-(3-pyridyl)-3,4-diaza-2,4-hexadiene and 1,4-bdc = benzene-1,4-dicarboxylate] were synthesized at room temperature. The structures of 1–5 were determined by single crystal X-ray diffraction analysis and were further characterized by elemental analysis, infrared spectroscopy (IR) and powder X-ray diffraction (PXRD). Compound 1 exhibits a one-dimensional (1D) chain structure with monodentate pendant 1,4-bdc ligands which further extend to a three-dimensional (3D) supramolecular structure by H-bonding and π⋯π interactions. Compound 2 displays a 4-connected two-dimensional (2D) framework with the point symbol {44·62}. Moreover, the 2D structure of 2 is also ultimately packed into 3D supramolecular frameworks through H-bonding and π–π stacking interactions. Compound 3 shows a 5-fold interpenetrated diamondoid net with 66 topology. Compound 4 is a 2D 3-connected net having a point symbol {63} and is extended to a supramolecular 3D structure through C–H⋯π and π⋯π interactions with lattice 3-bpdh ligands. Compound 5 features a 3-fold interpenetrated diamondoid net with 66 topology. The thermal stabilities and luminescent properties of 3–5 were also studied in detail. The complexes exhibit ligands based photoluminescence properties at room temperature.

Flexible dicarboxylate based pillar-layer metal organic frameworks: differences in structure and porosity by tuning the pyridyl based N,N′ linkers

Dicarboxylate supported metal organic hybrids of Co(II), Zn(II) and Cd(II) have been synthesized using two different pyridyl based N,N′ linkers having Schiff base functionalized site. The use of flexible dicarboxylate glutarate in designing such frameworks has created a marked diversity in topology. The different N,N′ donor linkers also played an active part in the channel modification in the synthesized MOFs. The structural and topological diversity has been analyzed from the single crystal X-ray structure. Five compounds, {[Co(azpy)(glut)]·(CH3OH)}n (1), {[Co(meazpy)(glut)(H2O)2]·(H2O)3}n (2), {[Zn(azpy)0.5(glut)(H2O)]·(azpy)0.5}n (3), {[Zn(meazpy)0.5(glut)(H2O)]·(H2O)2}n (4) and {[Cd(azpy)(glut)]·(CH3OH)}n (5), show porous structures with solvent accessible voids. The nature of the pores as well as the existence of lattice solvent molecules in 1 and 2 are different due to the use of a different pillar ligand in their fabrication. In case of 3 and 4 there are some nice effects of non-covalent interaction in the construction of their solid state structure, which has also originated by the change of pillar N,N′ donor linkers. Complex 5 is topologically as well as structurally similar to 1 forming a 2D-grid like structure. In {[Cd2(meazpy)2(glut)(NO3)]2}n (6) there is a formation of 2D sheets with the coordinated counter anion. Interestingly, here the sheets are disposed in a perpendicular fashion to each other and do not contain any solvent accessible void. Upon removal of the solvent molecules, the frameworks 1–5 show moderate CO2 and H2 uptake at 273 K and 77 K, respectively. The desolvated frameworks show different quantities of CO2 and H2 uptake which has been corroborated to their structures.

Syntheses, X-ray structures, catalytic activity and magnetic properties of two new coordination polymers of Co(II) and Ni(II) based on benzenedicarboxylate and linear N,N′-donor Schiff base linkers

Two isostructural coordination polymers based on Co(II) and Ni(II), {[M(azpy)3(p-bdc)2(H2O)4]·(CH3OH)2(H2O)3}n [where M = Co (1) and Ni (2); azpy = N,N′-bis-pyridin-4-ylmethylene-hydrazine and p-bdc = 1,4-benzenedicarboxylate], have been synthesized using mixed ligand systems at room temperature and characterized by single-crystal X-ray diffraction and other physicochemical methods. Structure determination reveals that both the complexes crystallize in the monoclinic space group C2/c and exhibit one-dimensional (1D) ladder like structures constructed by p-bdc and azpy ligands in which Schiff base (azpy) linkers serve as a bridging as well as pendent ligands. These pendent ligands are involved in H-bonding and π–π interactions with lattice water, methanol molecules and bridging azpy ligands, to form the 3D supramolecular structure. Notably, both the frameworks efficiently catalyze the Knoevenagel condensation reactions of a wide range of substituted benzaldehydes with active methylene compounds in heterogeneous medium under environmentally friendly conditions and the products were obtained in excellent yields. These catalysts were also found to exhibit excellent recyclability and re-usability without any significant loss of activity. A variable temperature magnetic study of both compounds was carried out and their magnetic properties justified on the basis of their crystal structure.

Eye-Catching Dual-Fluorescent Dynamic Metal-Organic Framework Senses Traces of Water: Experimental Findings and Theoretical Correlation.

A guest-dependent dynamic fivefold interpenetrated 3D porous metal-organic framework (MOF) of ZnII ions has been synthesized that exhibits selective carbon dioxide adsorption. Furthermore, the MOF shows excellent luminescence behavior, which is supported by a systematic study on the guest-responsive multicolor emission of a suspension of the MOF. The dual-emission behavior arises from the excited-state intramolecular proton transfer (ESIPT), and the compound also shows remarkable potential to detect traces of water in various organic solvents. The experimental observations were also painstakingly authenticated by using time-dependent density-functional-theory (DFT) calculations.

Pillared-bilayer porous coordination polymers of Zn(II): enhanced hydrophobicity of pore surface by changing the pillar functionality

Two new isostructural porous coordination polymers of Zn(II) {[Zn2(NH2-bdc)2(4-bpdb)]·(H2O)4}n (1) and {[Zn2(NH2-bdc)2(4-bpdh)]·(H2O)4}n (2) [4-bpdb = 1,4-bis-(4-pyridyl)-2,3-diaza-1,3-butadiene, 4-bpdh = 2,5-bis-(4-pyridyl)-3,4-diaza-2,4-hexadiene and NH2-bdc = 5-amino-1,3-benzenedicarboxylate] have been synthesized using a mixed ligand system by solvent diffusion and structurally characterized through single crystal X-ray diffraction, variable temperature powder X-ray diffraction and thermogravimetric analysis. Both the coordination polymers are constructed using linear Schiff base linkers of similar length having N–N base functionalities but the only difference is the presence of methyl groups in adjacent carbon atoms of the N–N group in the 4-bpdh ligand. Single-crystal structure analysis revealed that both compounds 1 and 2 have two-dimensional (2D) pillared-bilayer framework structures containing 1D channels (8.3 × 3.8 A2 for 1 and 8.0 × 1.6 A2 for 2) filled with lattice water molecules. Channel dimensions in 2 decrease due to the presence of methyl groups. The desolvated frameworks of 1 and 2 are rigid which is evidenced by variable temperature PXRD. Both the compounds show type-I CO2 uptake profiles and the differences in CO2 adsorption uptakes have been corroborated to their void space (27.1% for 1 and 17.1% for 2). Desolvated forms of compound 1 exhibit remarkably high water adsorption capacity even at low vapor pressure whereas desolvated forms of compound 2 show very low water vapor uptake, which could be ascribed to the hydrophobic nature of the pore surface of 2.

Formation of three new metal organic hybrids of Cd(II) with N,N′ donor spacer: an in situ perchlorate to chloride transformation

Three new metal–organic hybrids have been synthesized in a reaction of Cd(II) with 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene (3-bpdb) and disodium succinate (Na2suc). All three compounds, i.e., {[Cd(3-bpdb)(Cl)]·ClO4}n (1), {[Cd(3-bpdb)3(H2O)2]·(3-bpdb)(ClO4)2}n (2) and {[Cd(3-bpdb)(suc)(H2O)2]·(H2O)2}n (3) are characterized by single-crystal X-ray diffraction and other physicochemical methods. Structure determination reveals that 1 shows an α-polonium type 3D coordination network created by an exactly perpendicular Cl–Cd–Cl linkage. The framework of 1 contains 1D channels, which are filled with ClO4−. Compound 2 shows a 1D coordination structure with two bridging and two pendent 3-bpdb ligands. These pendent ligands are involved in H-bonding, π–π and C–H⋯π interactions with its coordinated water molecules and lattice 3-bpdb ligands, to form the 3D supramolecular structure. Compound 3 is a 2D 4-connected net with succinate and the 3-bpdb ligand and extended to 3D supramolecular architecture by H-bonding and π–π interactions. During the syntheses, an in situ chemical transformation of perchlorate to chloride has occurred along with the oxidation of imine to amide and the chlorides so produced are found integrated in compound 1, which facilitates the oxidation of imine in a very unprecedented way.

Dynamic metal–organic frameworks: syntheses, characterizations, sorption studies and their hydrolytic inter-conversion

Two metal–organic frameworks of Cd(II) from 3,4-pyridinedicarboxylate (3,4-pyrdc) and 1,2-bis(4-pyridyl)ethane (bpe) ligands, {[Cd(3,4-pyrdc)(bpe)(CH3OH)]·(H2O)}n (1) and {[Cd(3,4-pyrdc)(bpe)0.5(H2O)]·(H2O)}n (2) have been synthesized by changing the reaction medium. Compound 1 exhibited a 2D structure while compound 2 showed a 3D structure, which have both been revealed by single crystal X-ray studies. Both of the compounds showed interesting solvent mediated reversible structural transformations which have been established by exhaustive X-ray powder diffraction studies, elemental analysis, IR spectroscopy and thermogravimetric analysis. The desolvated form of the 2D framework (1) undergoes an irreversible structural transformation to form the 3D framework (2) upon soaking with water. The 2D to 3D transformation occurs through precise bond rotation and bond breaking which has been established by a GC–MS study. Sorption experiments with different gases and volatiles were performed for both the metal–organic frameworks and clearly indicated the differences in their inherent flexibility and transformability.

Synthesis, crystal structure and photo luminescent property of a 3D metal-organic hybrid of Cd(II) constructed by two different bridging carboxylate

AbstractA solvothermal reaction of cadmium (II) nitrate with succinic acid and isonicotinic acid creates a novel 3D metal-organic framework, [Cd3(isonicotinate)2(suc)2]n(1). Single crystal X-ray structure determination reveals that complex 1 posses two crystallographically independent Cd(II) centres. The succinate anion acts here as a heptadented ligand and binds five Cd(II) centre simultaneously. The heptacoordinated Cd(II) centres are oxo-bridged by succinate moiety and the hexacoordinated metal centres are terminally connected through four different succinate moiety to make the overall 2D sheet arrangement. In unit cell, the ratio of hexadented Cd(II) and heptadented Cd(II) is 1:2. The new compound was also characterized by luminescence spectra and compared with the luminescence spectra of the pure isonicotinic acid. Graphical AbstractA novel 3D metal–organic framework of Cd(II) has been synthesized by solvothermal reaction using two different carboxylate, succinate and isonicotinate ligands. The succinate anion acts as a heptadentate ligand and binds to five Cd(II) centers.