Ranjay K. Tiwari

H-bond supported coordination polymers of transition metal sulfites with different dimensionalities

Three new transition metal–sulfite coordination complexes namely [(C6N4H18)NaCo(SO3)2(H2O)3], (1), [(C3N2H10)2NaCo(SO3)2(H2O)2]·H2O, (2), and [(C6N4H18)Zn3(SO3)3], (3), have been synthesized under hydrothermal conditions in the presence of various organic amines where the amine behaves as an organic ligand. The complexes were characterized by PXRD, TGA and FTIR techniques. 1 shows the formation of a zero dimensional structure whereas 2 and 3 show two dimensional layer structures. The difference between 1 and 2 is due to the usage of different amines. The tetradentate amine in 1 dictates the coordination of sulfite groups in a cis-manner leading to the formation of a zero dimensional structure whereas in 2 the bidentate amine forces the sulfite group coordination in a trans-manner resulting in a two dimensional structure. In 3, the tetradentate amine caps one of the Zn centres, however the other two unique zinc ions coordinate with the sulfite anion to form interconnected cyclic dimers which gives a two dimensional layer structure. The subtle changes in the hydrogen bonding pattern and its consequence on the overall lattice to give a three dimensional network for 1 and 2 and two dimensional layer structure for 3 have been emphasized in detail.

Organically templated linear metal sulfites

Organically-templated linear zinc and manganese sulfites have been prepared under mild reaction conditions and structurally characterized by single crystal X-ray diffraction. The linear zinc sulfites, with the compositions, [(C3H10N)2][Zn(SO3)2], 1, [C3H12N2][Zn(SO3)2], 2, [C4H14N2][Zn(SO3)2], 3, [C6H18N2][Zn(SO3)2], 4 and [C4H12N2][Zn(SO3)2]·H2O, 5 possessing chain topologies consist of ZnO4 tetrahedra and SO3 pyramidal units forming four-membered rings which are connected through their vertices giving rise to 1D-chain structures. The linear manganese sulfite 6, with the composition [C4H12N2][Mn(SO3)2(H2O)2]·2H2O has kronkite type topology through corner sharing of four-membered rings formed by the MnO6 octahedron and SO3 pyramidal units. In all these structures the amine molecules are sitting between the interchain spaces. The compounds have been characterized by powder X-ray diffraction, infrared spectroscopy and thermogravimetric analysis.

Hybrid materials based on transition metal–BTC–benzimidazole: solvent assisted crystallographic and structural switching

Five transition metal–BTC–BIm based coordination polymers, namely [Zn2(HBTC)2(BIm)2(H2O)2]·(H2O)3, 1; [2-HABI]2[Zn2(BTC)2(2-ABI)(H2O)]·(H2O)5, 2; [Cu3(BTC)2(BIm)6][solvent], 3; [Co4(BTC)3(BIm)6][solvent], 4; and [(CH3CH2)2NH2][Zn(BTC)(BIm)]·(H2O), 5 have been synthesized and characterized using complementary techniques like single crystal X-ray analysis, powder X-ray diffraction (PXRD) and thermogravimetric analysis (TGA) (BTC = 1,3,5-benzene tricarboxylic acid, BIm = benzimidazole and 2-ABI = 2-aminobenzimidazole). Crystal structure analysis of these compounds showed that 1 forms a 1D chain, 2 and 3 have 2D layers while 4 and 5 have three-dimensional architectures. 3 forms a hexagonal bronze sheet, 4 has a three-dimensional network with embedded paddlewheel SBUs and helical assembly, and 5 crystallizes in a polar space group (Pna21) with 3D helical networks with adamantane-type topology. The dielectric properties of 5 showed that the dielectric constant rapidly decreases with an increase in frequency suggesting dipole relaxation at low frequencies.

Thermally induced 1D to 2D polymer conversion accompanied by major packing changes in single-crystal-to-single-crystal transformation

An unprecedented thermal response is observed in [(4,4′-bpe·2H+)(HSO4−)2] (1), a hydrogen-bonded 1D coordination polymer. While 1 was photostable to irradiation at 365 nm, upon heating at 70 °C for 1 h, it transformed into 1·ph, a 2D polymer, through single-crystal-to-single-crystal transformation (SCSCT). In this conversion, a series of bonds are broken and re-formed simultaneously, leading to major changes in the packing pattern which is quite rare in SCSCT.

CCDC 1431808: Experimental Crystal Structure Determination

Related Article: Ranjay K. Tiwari, Jitendra Kumar, J. N. Behera|2017|Dalton Trans.|46|15939|doi:10.1039/C7DT03073H

Open-framework metal sulfites and sulfite-oxalates based on honeycomb-like structures

In recent decades Open-framework materials are emerging area of study in materials chemistry, because of their huge and vast class of applications in areas such as sorption, magnetism, fuel cell, electrical conductivity, and catalysis. Furthermore, these materials exhibit attractive structural and topological diversities having usual H-bonding and coordination bonding. The study started with aluminosilicate zeolites, using metal and primary building units like silicate, phosphate, sulfate, metal phosphates, sulfates, and selenate etc. constitute an important family of open-framework structures. The sulfite based framework were very few explored due to the inherent instability of sulfite anion in acidic as well as hydrothermal conditions using organic amine as template, where the sulfur atom in sulfite ion is in the +4 oxidation state, which is relatively unstable under hydrothermal and acidic conditions and easily converted in +6 oxidation state and form sulfate ion. We were interested in exploring the missing amine template sulfite oxyanion and sulfite-oxalate hybrid materials with varying structure dimensionalities, and their various applications. Here we present the results of the investigations of metal sulfites employing transition metal with diverse structures and dimensionalities in presence of organic templates. The introduction of oxalate anion into the framework materials change the crystallographic signatures of the crystal lattice and adds additional structural complexity where the oxalate moiety acts as a ligand or bridging species. Thus, oxalate anion has been exploited in conjunction with sulfite and their results. Here we represent the synthesis and characterisation of a varying structural dimensionality of open-framework metal sulfites and metal sulfitesoxalates materials.