Amit Adhikary | University of Missouri Columbia (original) (raw)
Papers by Amit Adhikary
ChemInform, Nov 8, 2013
Heteroatom-Guided, Palladium-Catalyzed, Site-Selective C-H Arylation of 4H-Chromenes: Diastereose... more Heteroatom-Guided, Palladium-Catalyzed, Site-Selective C-H Arylation of 4H-Chromenes: Diastereoselective Assembly of the Core Structure of Myristinin B Through Dual C-H Functionalization.-Conditions for the site-selective coupling of 4-substituted chromenes with aryliodides as well as aryl boronic acids are elaborated which provide the corresponding 2-arylated derivatives. In contrast, the transformation of 4,4-disubstituted chromenes with aryliodides delivers 3,3-disubstituted 2-arylidene-2,3-dihydrobenzofuran derivatives, whereas their reaction with aryl boronic acids affords the corresponding 3-arylated chromene derivatives. Additionally, the reaction of 4-substituted and 4,4-disubstituted chromene derivatives with substituted arenes is studied, and provides 2-arylated chromenes or 2-arylidene-2,3-dihydrobenzofuran derivatives, respectively, albeit as a mixture of ortho-, meta-, and para-arylated compounds.-(
Polyhedron, Mar 1, 2019
The syntheses, crystal structures, magnetic properties and DFT calculations of four Cu(II) comple... more The syntheses, crystal structures, magnetic properties and DFT calculations of four Cu(II) complexes of the formula [{Cu(2,2´-bpy)(HCPCA)}(H 2 O) 2 ].3H 2 O (1), [Cu(dmbp)(HCPCA)] (2), [Cu(phen)(HCPCA)].H 2 O (3) and [Cu(phen)(CPCA)] 2 .DMF (4) [H 2 CPCA = 3-(3-carboxyphenyl)-1H-pyrazole-5-carboxylic acid, phen = 1,10-phenanthroline] are reported here. Our main focus was to design ta ferromagnetic complex and therefore concentrated on the mononuclear and binuclear copper complexes 3 and 4. In complex 3 the pyrazole unit of the H 2 CPCA ligand binds (as HCPCA-) in a monodentate fashion to form the mononuclear complex, and in complex 4 the pyrazole unit of the H 2 CPCA ligand binds (as CPCA 2-) in a bidentate fashion to form a binuclear complex, creating a near orthogonal orientation between the two Cu(II) ions. Temperature dependent magnetic susceptibility measurements show the appearance of weak ferromagnetic interactions for complex 4, whereas complex 3 shows paramagnetic behavior. The results are in excellent agreement with theoretical Broken Symmetry-DFT calculations.
Crystal Growth & Design, Jul 29, 2020
We report herein synthesis, characterization and properties of some metal directed architectures ... more We report herein synthesis, characterization and properties of some metal directed architectures using a new asymmetric, semi-rigid and bis-chelating pyridine-pyrazole based ligand, {N'-(amino (pyrimidin-2-yl)methylene)-3-(pyridin-2-yl)-1H-pyrazole-5-carbohydrazide (H 2 APPC)}. The H 2 APPC ligand forms multinuclear cage complexes with different transition metal salts ranging from discrete mononuclear complex to nonanuclear with different kind of network topology. The semi-rigid ligand molecule not only changes the conformation but also exhibit variable coordination behavior, depending on the metal ions used. For instance, the reaction of manganese salt with H 2 APPC results in a truncated [3×3] grid network whereas the nickel salt forms a highly unusual hexanuclear cage complex. Interestingly, in presence of copper salt, H 2 APPC forms a different kind of structure along with an in-situ generated new ligand. The zinc salts form a mononuclear complex. Most interestingly, reaction with cadmium salts leads to an intriguing [3×3] grid network, with a highly unusual occurrence of multiple variant of coordination environments around the metal centres. It is imperative to note here that above display of metal-directed architectures are quite uncommon for an asymmetric semi-rigid ligand and cadmium complex shows four kind of coordination geometry which is not known in the literature, to the best of our knowledge. The variable temperature magnetic measurements of manganese, nickel and copper complex showed strong antiferromagnetic interaction between the neighboring metal centers. Furthermore, the Cd 9 framework showed promising solvent dependent luminescent properties.
Inorganic Chemistry, Nov 16, 2020
A novel metal-organic framework (MOF), [Zn2(tdca)2(bppd)2]·2DMF, has been synthesized solvotherma... more A novel metal-organic framework (MOF), [Zn2(tdca)2(bppd)2]·2DMF, has been synthesized solvothermally using the ligand thiophene-2,5-dicarboxylic acid (H2tdca), coligand N,N'-bis(4-pyridylmethylene)-1,4-benzenediamine (bppd), and Zn(NO3)2. Single crystal X-ray crystallography reveals that the titled MOF is a three-dimensional pillared-layered MOF. A layer is constituted by a Zn(tdca) unit, and the layers are stabilized by the long hydrocarbon coligand, bppd, which acts as a pillar. A rectangular pore size of 11.42 × 8.12 Å2 is found in the framework. The porous framework is found to be an excellent fluorescence sensor for the detection of toxic Cd2+ ion. The sensor shows high selectivity and sensitivity and a quick response toward Cd2+. The synthesized MOF is able to not only detect cadmium ions but also adsorb iodine in the gas phase. The MOF can adsorb ∼66% iodine, verified by thiosulfate-iodine titration and TG analysis. Adsorbed iodine can also be removed easily in acetonitrile as well as in n-hexane, which shows that iodine can be reversibly loaded as well as unloaded into the framework.
Dalton Transactions, 2021
In this contribution, we report the synthesis, characterization and luminescence–magnetic propert... more In this contribution, we report the synthesis, characterization and luminescence–magnetic properties of Ln-clusters (Ln = Gd3+, Eu3+ and Tb3+) using a new pyridine–pyrazole functionalized ligand fitted with a chromophoric phenanthroline backbone. We have applied the luminescence property of clusters for cancer cell imaging.
Dalton Transactions, 2013
Synthesis of [Gd(C 4 O 4)(OH)(H 2 O) 4 ] n : 3ml 0.1(M) methanolic solution of Gd(NO 3).6H 2 O wa... more Synthesis of [Gd(C 4 O 4)(OH)(H 2 O) 4 ] n : 3ml 0.1(M) methanolic solution of Gd(NO 3).6H 2 O was carefully layered above the 3ml 0.1(M) aqueous solution of lithium squarate in a layering tube for slow solvent diffusion. The tube was gently kept at room temperature for few weeks. Colourless shiny diffraction quality needle like crystals were appeared at the junction. Selected
New Journal of Chemistry, 2023
The pseudo-zero-order kinetics of the catecholase-like activity of biologically active linear tri... more The pseudo-zero-order kinetics of the catecholase-like activity of biologically active linear trinuclear mixed-valence manganese complexes have been explored; the formation of singlet oxygen is thought to be the rate-limiting step.
Materials advances, 2022
The present work reports the design and synthesis of a low molecular weight gelator (LMWG), namel... more The present work reports the design and synthesis of a low molecular weight gelator (LMWG), namely 1-(3-(pyridin-2-yl)-1H-pyrazole-5-carboylimino)ethyl)phenyl)ethylidene)-3-(pyridin-2-yl)-1H-pyrazole-5carbohydrazide (H 3 BPDP). H 3 BPDP acts as a gelator to encapsulate the toxic heavy metal ions Pb(II), Cd(II) and Hg(II) and forms metal-organic gels (MOGs). Microscopic analyses such as SEM and TEM of the MOGs revealed intertwining fibrous networks for Cd and Hg, whereas interesting nanoscale metalorganic particles (NMOPs) were formed with Pb-MOG. After heating the Pb-MOG for a few hours and keeping the solution for slow evaporation for a few days, remarkably single crystals were grown. Single-crystal X-ray analysis indeed confirmed the encapsulation of Pb 2+ by the gelator, H 3 BPDP, and a two-dimensional coordination polymer of composition [Pb 5 (BPDP) 2 (NO 3) 4 (DMF)] n was observed. Moreover, EDAX analysis also confirmed the encapsulation of Pb, Cd, and Hg elements from their respective xerogels. The formation of MOGs with the toxic metals was also monitored by 1 H NMR titration and ligand participation in the formation of the metal-N bond was clearly perceptible by monitoring the N-H proton. The MOGs exhibited sol-gel transformation by applying thermo-, chemical, pH-and mechano-stimuli. Besides that, the xerogels of the Cd-based MOG and Pb-based MOG have shown remarkable efficiency (480%) to adsorb the toxic methyl orange (MO) dye, which may be utilized in wastewater treatment.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Dalton Transactions, 2022
We report herein an aesthetically pleasing hexanuclear Nd6 molecular butterfly using a rather non... more We report herein an aesthetically pleasing hexanuclear Nd6 molecular butterfly using a rather nonconventional N-rich pyridyl-pyrazolyl based ligand and their concomitant SMM and MCE properties along with elusive electronic properties.
Herein, we report the syntheses, structure, Na-ion conductivity, and theoretical investigation of... more Herein, we report the syntheses, structure, Na-ion conductivity, and theoretical investigation of two moisture stable quaternary compounds, Na3ZnGaQ4 (Q = S, Se). These compounds are synthesized using high-temperature solid-state synthesis routes employing polychalcogenide flux or by metathesis reactions. The crystal structure of these compounds is built up of a three-dimensional (3-D) network of corner-shared supertetrahedral (T2) units, where two such 3-D networks are interlocked. The d-block metal and the main group metal, Ga, occupy the same crystallographic site with a 1:1 ratio, making it a rare form of building unit. Band structure calculations show that both the compounds are wide band gap semiconductors with band gaps of 2.25 and 1.61 eV, respectively, for Na3ZnGaS4 (I) and Na3ZnGaSe4 (II), which are slightly underestimated compared to experimentally determined band gaps of 3.0 and 1.90 eV, respectively. I and II possess ionic conductivities of 3.74 x 10-4 and 0.12 mS/cm with activation energies of 0.42 and 0.38 eV, respectively, at 30 °C. Interestingly, I shows a significantly high ionic conductivity of 0.13 mS/cm at 30 °C upon exposure to air, which could be due to water adsorption on the surface or occlusion in the grain boundaries. Assuming the vacancy-Assisted diffusion mechanism for ionic conductance, this difference is consistent with the difference on vacancy formation energies in these compounds, as predicted by DFT calculations. The bond valence sum map indicates that in both structures, the lowest energy diffusion path is one dimensional and it is along the c axis of the unit cell
![Research paper thumbnail of Designing Multifunctional MOFs Using the Inorganic Motif [Cu3(μ3-OH)(μ-Pyz)] as an SBU and Their Properties](https://attachments.academia-assets.com/109808682/thumbnails/1.jpg)
](Crystal Growth & Design, 2018
Crystal Growth & Design, 2015
The complexation reactions of a tripodal chelating ligand, [3,5-bis(2-amino-ethyl)-[1,3,5]triazin... more The complexation reactions of a tripodal chelating ligand, [3,5-bis(2-amino-ethyl)-[1,3,5]triazinan-1-yl]-methanol (L), which is produced by the in situ transformation of 1,3,6,8-tetraazatricyclo[4.4.1.1 3,8 ]dodecane (L 1) with Ni(NO 3) 2 •6H 2 O has been explored in the presence of ammonium salts of inorganic and organic anions. These reactions resulted in four crystalline complexes [Ni 4 (L) 2 (μ 3-OH) 2 (NCS) 4 ]•4H 2 O (1), [Ni 4 (L) 2 (μ 2-N 3) 4 (N 3) 2 ]•2H 2 O (2), [Ni 8 (L) 4 (μ 3-OH) 4 (BDC) 3 (H 2 O) 4 ]• BDC•28(H 2 O) (3, BDC = 1,4-benzene dicarboxylate) and {[Ni 4 (L) 2 (μ 3-OH) 2 (NDS) 2 (H 2 O) 2 ]•NDS•11(H 2 O)} n (4, NDS = naphthalene-1,5-disulfonate). The crystal structure analyses of 1−4 reveal that all contain Ni(II) clusters, which act as secondary building units to generate higher order aggregates. The complexes 1, 3, and 4 contain exclusively Ni 4 cubane units: a discrete cubane in 1, a dimer of cubanes linked by BDC in 3, and cubanes linked in one dimension by NDS to form a 1D-coordination polymer in 4. Interestingly, complex 2 exhibits an open dicubane with two missing vertices. Although a plethora of water molecules had been included in their crystal lattices, the crystals were found to be stable even at room temperature. The water molecules govern the overall crystal packing by the formation of strong hydrogen bonds and clusters. Large clusters of water such as (H 2 O) 28 and (H 2 O) 16 were observed in 3 and 4, respectively, while dimers of water were observed in 1 and 2. Magnetic susceptibility (χ M) measurements in the temperature range of 2−300 K on 1−3 reveal that the metal centers are ferromagnetically coupled in all three depending on their respective exchange pathways. Interestingly, the room temperature (300 K) χ M T values increase as the molecular aggregation increases from discrete cubane (5.5 cm 3 K mol −1) to face sharing open dicubane (6.21 cm 3 K mol −1) to connected dicubane (11.36 cm 3 K mol −1). The modes of bridging by − OH, N 3 − , and BDC and their bond angles with paramagnetic Ni(II) centers clearly explained the overall ferromagnetism operating in the spin clusters.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
ChemInform, Nov 8, 2013
Heteroatom-Guided, Palladium-Catalyzed, Site-Selective C-H Arylation of 4H-Chromenes: Diastereose... more Heteroatom-Guided, Palladium-Catalyzed, Site-Selective C-H Arylation of 4H-Chromenes: Diastereoselective Assembly of the Core Structure of Myristinin B Through Dual C-H Functionalization.-Conditions for the site-selective coupling of 4-substituted chromenes with aryliodides as well as aryl boronic acids are elaborated which provide the corresponding 2-arylated derivatives. In contrast, the transformation of 4,4-disubstituted chromenes with aryliodides delivers 3,3-disubstituted 2-arylidene-2,3-dihydrobenzofuran derivatives, whereas their reaction with aryl boronic acids affords the corresponding 3-arylated chromene derivatives. Additionally, the reaction of 4-substituted and 4,4-disubstituted chromene derivatives with substituted arenes is studied, and provides 2-arylated chromenes or 2-arylidene-2,3-dihydrobenzofuran derivatives, respectively, albeit as a mixture of ortho-, meta-, and para-arylated compounds.-(
Polyhedron, Mar 1, 2019
The syntheses, crystal structures, magnetic properties and DFT calculations of four Cu(II) comple... more The syntheses, crystal structures, magnetic properties and DFT calculations of four Cu(II) complexes of the formula [{Cu(2,2´-bpy)(HCPCA)}(H 2 O) 2 ].3H 2 O (1), [Cu(dmbp)(HCPCA)] (2), [Cu(phen)(HCPCA)].H 2 O (3) and [Cu(phen)(CPCA)] 2 .DMF (4) [H 2 CPCA = 3-(3-carboxyphenyl)-1H-pyrazole-5-carboxylic acid, phen = 1,10-phenanthroline] are reported here. Our main focus was to design ta ferromagnetic complex and therefore concentrated on the mononuclear and binuclear copper complexes 3 and 4. In complex 3 the pyrazole unit of the H 2 CPCA ligand binds (as HCPCA-) in a monodentate fashion to form the mononuclear complex, and in complex 4 the pyrazole unit of the H 2 CPCA ligand binds (as CPCA 2-) in a bidentate fashion to form a binuclear complex, creating a near orthogonal orientation between the two Cu(II) ions. Temperature dependent magnetic susceptibility measurements show the appearance of weak ferromagnetic interactions for complex 4, whereas complex 3 shows paramagnetic behavior. The results are in excellent agreement with theoretical Broken Symmetry-DFT calculations.
Crystal Growth & Design, Jul 29, 2020
We report herein synthesis, characterization and properties of some metal directed architectures ... more We report herein synthesis, characterization and properties of some metal directed architectures using a new asymmetric, semi-rigid and bis-chelating pyridine-pyrazole based ligand, {N'-(amino (pyrimidin-2-yl)methylene)-3-(pyridin-2-yl)-1H-pyrazole-5-carbohydrazide (H 2 APPC)}. The H 2 APPC ligand forms multinuclear cage complexes with different transition metal salts ranging from discrete mononuclear complex to nonanuclear with different kind of network topology. The semi-rigid ligand molecule not only changes the conformation but also exhibit variable coordination behavior, depending on the metal ions used. For instance, the reaction of manganese salt with H 2 APPC results in a truncated [3×3] grid network whereas the nickel salt forms a highly unusual hexanuclear cage complex. Interestingly, in presence of copper salt, H 2 APPC forms a different kind of structure along with an in-situ generated new ligand. The zinc salts form a mononuclear complex. Most interestingly, reaction with cadmium salts leads to an intriguing [3×3] grid network, with a highly unusual occurrence of multiple variant of coordination environments around the metal centres. It is imperative to note here that above display of metal-directed architectures are quite uncommon for an asymmetric semi-rigid ligand and cadmium complex shows four kind of coordination geometry which is not known in the literature, to the best of our knowledge. The variable temperature magnetic measurements of manganese, nickel and copper complex showed strong antiferromagnetic interaction between the neighboring metal centers. Furthermore, the Cd 9 framework showed promising solvent dependent luminescent properties.
Inorganic Chemistry, Nov 16, 2020
A novel metal-organic framework (MOF), [Zn2(tdca)2(bppd)2]·2DMF, has been synthesized solvotherma... more A novel metal-organic framework (MOF), [Zn2(tdca)2(bppd)2]·2DMF, has been synthesized solvothermally using the ligand thiophene-2,5-dicarboxylic acid (H2tdca), coligand N,N'-bis(4-pyridylmethylene)-1,4-benzenediamine (bppd), and Zn(NO3)2. Single crystal X-ray crystallography reveals that the titled MOF is a three-dimensional pillared-layered MOF. A layer is constituted by a Zn(tdca) unit, and the layers are stabilized by the long hydrocarbon coligand, bppd, which acts as a pillar. A rectangular pore size of 11.42 × 8.12 Å2 is found in the framework. The porous framework is found to be an excellent fluorescence sensor for the detection of toxic Cd2+ ion. The sensor shows high selectivity and sensitivity and a quick response toward Cd2+. The synthesized MOF is able to not only detect cadmium ions but also adsorb iodine in the gas phase. The MOF can adsorb ∼66% iodine, verified by thiosulfate-iodine titration and TG analysis. Adsorbed iodine can also be removed easily in acetonitrile as well as in n-hexane, which shows that iodine can be reversibly loaded as well as unloaded into the framework.
Dalton Transactions, 2021
In this contribution, we report the synthesis, characterization and luminescence–magnetic propert... more In this contribution, we report the synthesis, characterization and luminescence–magnetic properties of Ln-clusters (Ln = Gd3+, Eu3+ and Tb3+) using a new pyridine–pyrazole functionalized ligand fitted with a chromophoric phenanthroline backbone. We have applied the luminescence property of clusters for cancer cell imaging.
Dalton Transactions, 2013
Synthesis of [Gd(C 4 O 4)(OH)(H 2 O) 4 ] n : 3ml 0.1(M) methanolic solution of Gd(NO 3).6H 2 O wa... more Synthesis of [Gd(C 4 O 4)(OH)(H 2 O) 4 ] n : 3ml 0.1(M) methanolic solution of Gd(NO 3).6H 2 O was carefully layered above the 3ml 0.1(M) aqueous solution of lithium squarate in a layering tube for slow solvent diffusion. The tube was gently kept at room temperature for few weeks. Colourless shiny diffraction quality needle like crystals were appeared at the junction. Selected
New Journal of Chemistry, 2023
The pseudo-zero-order kinetics of the catecholase-like activity of biologically active linear tri... more The pseudo-zero-order kinetics of the catecholase-like activity of biologically active linear trinuclear mixed-valence manganese complexes have been explored; the formation of singlet oxygen is thought to be the rate-limiting step.
Materials advances, 2022
The present work reports the design and synthesis of a low molecular weight gelator (LMWG), namel... more The present work reports the design and synthesis of a low molecular weight gelator (LMWG), namely 1-(3-(pyridin-2-yl)-1H-pyrazole-5-carboylimino)ethyl)phenyl)ethylidene)-3-(pyridin-2-yl)-1H-pyrazole-5carbohydrazide (H 3 BPDP). H 3 BPDP acts as a gelator to encapsulate the toxic heavy metal ions Pb(II), Cd(II) and Hg(II) and forms metal-organic gels (MOGs). Microscopic analyses such as SEM and TEM of the MOGs revealed intertwining fibrous networks for Cd and Hg, whereas interesting nanoscale metalorganic particles (NMOPs) were formed with Pb-MOG. After heating the Pb-MOG for a few hours and keeping the solution for slow evaporation for a few days, remarkably single crystals were grown. Single-crystal X-ray analysis indeed confirmed the encapsulation of Pb 2+ by the gelator, H 3 BPDP, and a two-dimensional coordination polymer of composition [Pb 5 (BPDP) 2 (NO 3) 4 (DMF)] n was observed. Moreover, EDAX analysis also confirmed the encapsulation of Pb, Cd, and Hg elements from their respective xerogels. The formation of MOGs with the toxic metals was also monitored by 1 H NMR titration and ligand participation in the formation of the metal-N bond was clearly perceptible by monitoring the N-H proton. The MOGs exhibited sol-gel transformation by applying thermo-, chemical, pH-and mechano-stimuli. Besides that, the xerogels of the Cd-based MOG and Pb-based MOG have shown remarkable efficiency (480%) to adsorb the toxic methyl orange (MO) dye, which may be utilized in wastewater treatment.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Dalton Transactions, 2022
We report herein an aesthetically pleasing hexanuclear Nd6 molecular butterfly using a rather non... more We report herein an aesthetically pleasing hexanuclear Nd6 molecular butterfly using a rather nonconventional N-rich pyridyl-pyrazolyl based ligand and their concomitant SMM and MCE properties along with elusive electronic properties.
Herein, we report the syntheses, structure, Na-ion conductivity, and theoretical investigation of... more Herein, we report the syntheses, structure, Na-ion conductivity, and theoretical investigation of two moisture stable quaternary compounds, Na3ZnGaQ4 (Q = S, Se). These compounds are synthesized using high-temperature solid-state synthesis routes employing polychalcogenide flux or by metathesis reactions. The crystal structure of these compounds is built up of a three-dimensional (3-D) network of corner-shared supertetrahedral (T2) units, where two such 3-D networks are interlocked. The d-block metal and the main group metal, Ga, occupy the same crystallographic site with a 1:1 ratio, making it a rare form of building unit. Band structure calculations show that both the compounds are wide band gap semiconductors with band gaps of 2.25 and 1.61 eV, respectively, for Na3ZnGaS4 (I) and Na3ZnGaSe4 (II), which are slightly underestimated compared to experimentally determined band gaps of 3.0 and 1.90 eV, respectively. I and II possess ionic conductivities of 3.74 x 10-4 and 0.12 mS/cm with activation energies of 0.42 and 0.38 eV, respectively, at 30 °C. Interestingly, I shows a significantly high ionic conductivity of 0.13 mS/cm at 30 °C upon exposure to air, which could be due to water adsorption on the surface or occlusion in the grain boundaries. Assuming the vacancy-Assisted diffusion mechanism for ionic conductance, this difference is consistent with the difference on vacancy formation energies in these compounds, as predicted by DFT calculations. The bond valence sum map indicates that in both structures, the lowest energy diffusion path is one dimensional and it is along the c axis of the unit cell
Crystal Growth & Design, 2018
Crystal Growth & Design, 2015
The complexation reactions of a tripodal chelating ligand, [3,5-bis(2-amino-ethyl)-[1,3,5]triazin... more The complexation reactions of a tripodal chelating ligand, [3,5-bis(2-amino-ethyl)-[1,3,5]triazinan-1-yl]-methanol (L), which is produced by the in situ transformation of 1,3,6,8-tetraazatricyclo[4.4.1.1 3,8 ]dodecane (L 1) with Ni(NO 3) 2 •6H 2 O has been explored in the presence of ammonium salts of inorganic and organic anions. These reactions resulted in four crystalline complexes [Ni 4 (L) 2 (μ 3-OH) 2 (NCS) 4 ]•4H 2 O (1), [Ni 4 (L) 2 (μ 2-N 3) 4 (N 3) 2 ]•2H 2 O (2), [Ni 8 (L) 4 (μ 3-OH) 4 (BDC) 3 (H 2 O) 4 ]• BDC•28(H 2 O) (3, BDC = 1,4-benzene dicarboxylate) and {[Ni 4 (L) 2 (μ 3-OH) 2 (NDS) 2 (H 2 O) 2 ]•NDS•11(H 2 O)} n (4, NDS = naphthalene-1,5-disulfonate). The crystal structure analyses of 1−4 reveal that all contain Ni(II) clusters, which act as secondary building units to generate higher order aggregates. The complexes 1, 3, and 4 contain exclusively Ni 4 cubane units: a discrete cubane in 1, a dimer of cubanes linked by BDC in 3, and cubanes linked in one dimension by NDS to form a 1D-coordination polymer in 4. Interestingly, complex 2 exhibits an open dicubane with two missing vertices. Although a plethora of water molecules had been included in their crystal lattices, the crystals were found to be stable even at room temperature. The water molecules govern the overall crystal packing by the formation of strong hydrogen bonds and clusters. Large clusters of water such as (H 2 O) 28 and (H 2 O) 16 were observed in 3 and 4, respectively, while dimers of water were observed in 1 and 2. Magnetic susceptibility (χ M) measurements in the temperature range of 2−300 K on 1−3 reveal that the metal centers are ferromagnetically coupled in all three depending on their respective exchange pathways. Interestingly, the room temperature (300 K) χ M T values increase as the molecular aggregation increases from discrete cubane (5.5 cm 3 K mol −1) to face sharing open dicubane (6.21 cm 3 K mol −1) to connected dicubane (11.36 cm 3 K mol −1). The modes of bridging by − OH, N 3 − , and BDC and their bond angles with paramagnetic Ni(II) centers clearly explained the overall ferromagnetism operating in the spin clusters.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.