Satirtha Sengupta

Identification of a robust and reproducible noncluster-type SBU: effect of coexistent groups on network topologies, helicity, and properties

The present work is part of our ongoing quest for a robust and reproducible noncluster-type secondary building unit (SBU) using pyrazole based ditopic ligands and benzene polycarboxylic acids. We report here the construction of a series of Zn(II) coordination polymers using a tailor-made SBU, designed with the proper utilization of the hydrogen bonds of a pyrazole-based ligand 4,4′-methylene-bispyrazole (H2MBP) and isophthalic acid (H2IPA), and its derivatives (R-H2IPA; R = OH, OCH3, CH3, tBu, Br, I, NH2, N3). The results demonstrate that the substituent effect of R-isophthalates does play a decisive role in directing the structural assemblies of this system. One of the promising features of the 2D networks of this series is the presence of SBU-based helical motifs, which by and large remain elusive despite the plethora of reports on various SBU based networks. Throughout the series, hydrogen bonds, π–π interactions and other intermolecular interactions play a crucial role in stabilizing the resulting networks. Furthermore, some of these complexes exhibit some interesting photoluminescent properties in the solid state.

Construction of helical networks by using multiple V-shaped mixed ligand systems

Helical coordination polymers constructed from multiple ligand systems are not common despite the plethora of recent reports on helical networks. We report here the construction of a series of mixed ligand based helical coordination polymers showing metal dependent architecture. The strategy of using a combination of ligand molecules, each capable of forming helical networks, is novel and should enable us to design helical MOFs of interesting topology.

A novel gel-based approach to wastewater treatment – unique one-shot solution to potentially toxic metal and dye removal problems

This communication reports the development of a unique gel-based adsorbent for wastewater treatment using a new low molecular weight gelator. The most interesting aspect of this technique is that the ligand not only gelled potentially toxic metals, like lead and cadmium, but that it also simultaneously adsorbed toxic dyes, like methyl orange, from an aqueous solution. This offers a one-shot solution to two major water purification problems.

Elusive nanoscale metal-organic-particle-supported metallogel formation using a nonconventional chelating pyridine-pyrazole-based bis-amide ligand.

Support group: A rare case of metallogel formation supported by nanoscale metal-organic particles by using a nonconventional ditopic chelating ligand is reported.

Silver-promoted gelation studies of an unorthodox chelating tripodal pyridine–pyrazole-based ligand: templated growth of catalytic silver nanoparticles, gas and dye adsorption

A novel tripodal pyridine–pyrazole based tris amide ligand, namely, N1,N3,N5-tris(3-(pyridin-2-yl)-1H-pyrazol-5-yl)benzene-1,3,5-tricarboxamide was synthesized. The ligand acts as a promising low molecular weight gelator that gels silver salts in presence of water. The gels formed were found to be highly stable to heat and stress. Moreover, silver ions not only act as a gelling agent but also participate in nanoparticulate formation. The three-dimensional ligand–silver gel matrix serves as an excellent platform for the growth of these silver nanoparticles. The gels were characterized thoroughly using IR spectroscopy, UV-visible spectroscopy, SEM, TEM and rheological studies. TEM pictures revealed the nanoparticles to be attached exclusively onto the gel fibres confirming template formation. The silver nanoparticles not only provide high strength and stability to the gel network but also show excellent catalytic properties in reducing 4-nitrophenol and Methylene Blue dye in presence of sodium borohydride. In addition to the catalytic properties, xerogels displayed gas and dye adsorption properties.

Construction of Co(II) coordination polymers comprising of helical units using a flexible pyrazole based ligand

1H-Pyrazole based molecules are potentially important in crystal engineering because of their ability to play a dual role in metal coordination as well as hydrogen bond formation using an in-built hydrogen bonding site. We report here the construction of a series of coordination polymers using a flexible pyrazole based ditopic ligand and different benzene polycarboxylic acids as auxiliary ligands. For all the structures, hydrogen bonding and π–π stacking were found to be instrumental in bringing additional stability to the self-assembly of these polymeric networks. Furthermore, we have successfully demonstrated the strategy of introducing helicity in the resultant polymeric network using a V-shaped ligand, H2MBP for the present work.

A novel low molecular weight supergelator showing an excellent gas adsorption, dye adsorption, self-sustaining and chemosensing properties in the gel state

In this manuscript we have described the role of a novel pyridine–pyrazole based bis amide molecule namely N1,N3-bis[5-(pyridin-2-yl)-1H-pyrazole-3-yl]-terephthalamide (BPPTP) which acts as a supergelator in forming very strong gels with copper triflate at a concentration as low as 0.3 wt%. The gel was found to be highly stable towards heat, mineral acids and mechanical stress thus showing self-sustainability. The xerogel showed not only high N2 gas sorption properties seldom reported for metallogels, but also good toxic dye sorption and rare amine sensing properties in gel state.

Influence of chloro⋯chloro interaction and π–π stacking in 3D supramolecular framework construction

A series of 1D and 2D coordination polymers have been synthesized under solvothermal conditions using a terminal ligand, 3,5,6-trichlorosalicylic acid (H2TCSA) and different bipyridine based ligands, 2,2′-bipyridyl (2,2′-BIPY), 4,4′-bipyridyl (4,4′-BIPY), 4,4′-trimethylene bipyridine (TMBP) and trans-1,2-bis(4-pyridyl)-ethylene (TBPE). The major aim of this work was to study the influence of weak interactions in constructing 3D supramolecular frameworks. A two-step crystal engineering strategy has been adopted for generating 3D supramolecular frameworks. Firstly, various lower dimensional coordination networks have been achieved and then 3D supramolecular frameworks were constructed from the self-assembly of these networks via weak intermolecular interactions among the organic parts. The latter was achieved with the usage of ligand systems that are devoid of any conventional hydrogen bonding functional group. On the other hand, employment of a terminal ligand serves the purpose of generating different lower dimensional architectures, ranging from discrete zero dimensional coordination complexes to 1D, 2D coordination polymeric networks. We report herein, two 0D complexes, [Zn(HTCSA)2(TBPE)2] (1), [{Zn(TCSA)(2,2′-BIPY)}4] (2), five 1D coordination polymers, [Zn(TCSA)(4,4′-BIPY)0.5(DMF)]n(3), [Zn(HTCSA)2(4,4′-BIPY)]n(4), [Zn(HTCSA)2(TMBP)]n(5), [Zn(HTCSA)2(TMBP)]n (6), [Zn(HTCSA)2(TBPE)(H2O)]n (7), and two 2D polymeric networks, [Zn(TCSA)(4,4′-BIPY)]n (8) and [{Zn(TCSA)(TBPE)}·(TBPE)]n (9), and two related cobalt and nickel complexes, [{Co(TCSA)(TBPE)}·(TBPE)]n (10) and [Ni(HTCSA)(TBPE)1.5·(NO3)]n (11). For all the structures, π–π stacking and halogen bonding were found to be instrumental in bringing the additional dimensions to the self-assembly of the lower dimensional networks and lead to diverse 3D supramolecular frameworks.