Mrinalini G. Walawalkar

Extended metal-organic solids based on benzenepolycarboxylic and aminobenzoic acids

This article describes the recent results obtained in our laboratory on the interaction of polyfunctional ligands with divalent alkaline earth metal ions and a few divalent transition metal ions. Treatment of MC12·nH2O (M = Mg, Ca, Sr or Ba) with 2-amino benzoic acid leads to the formation of complexes [Mg(2-aba)2] (1), [Ca(2-aba)2(OH2)3]∞ (2), [Sr(2-aba)2(OH2)22·H2O)]∞ (3), [Ba(2-aba)2(OH2)]∞ (4), respectively. While the calcium ions in2 are hepta-coordinated, the strontium and barium ions in3 and4 reveal a coordination number of nine apart from additional metal-metal interactions. Apart from the carboxylate functionality, the amino group also binds to the metal centres in the case of strontium and barium complexes3 and4. Complexes [Mg(H2O)6(4-aba)2·2H2O] (5), [Ca(4-aba)2(H2O)2] (6) prepared from 4-aminobenzoic acid reveal more open or layered structures. Interaction of 2-mercaptobenzoic acid with MCl2·6H2O (M = Mg, Ca), however, leads to the oxidation of the thiol group resulting in the disulphide 2,2′ -dithiobis(benzoic acid). New metal-organic framework based hydrogen-bonded porous solids [M(btec) (OH2)4n·n(C4H12N2)·4nH2O] (btec = 1,2,4,5-benzene tetracarboxylate) (M = Co9; Ni10; Zn11) have been synthesized from 1,2,4,5-benzene tetracarboxylic acid in the presence of piperazine. These compounds are made up of extensively hydrogen-bonded alternating layers of anionic M-btec co-ordination polymer and piperazinium cations. Compounds2- 11 described herein form polymeric networks in the solid-state with the aid of different coordinating capabilities of the carboxylate anions hydrogen bonding interactions.

Molecular Aluminophosphonate: Model Compound for the Isoelectronic Double‐Six‐Ring (D6R) Secondary Building Unit of Zeolites

The reaction of tert-butylphosphonic acid with equimolar quantities of AlMe3 in THF/n-hexane yields a mixture of [MeAlO3PtBu]6 (1) and [MeAlO3PtBu]4 (2). The molecular structure of 1 resembles the D6R building units found in aluminophosphates. The central core of the Al6O18P6 polyhedron can be described as a cylindrical drum. By tailoring the alkyl groups on aluminum and phosphorus, it is possible to generate bigger building units of aluminophosphate molecular sieves.

Molecular zinc phosphonates: synthesis and X-ray crystal structures of [{(ZnMe)4(THF)2}{tBuPO3}2] and [{(ZnEt)3(Zn(THF))3}{tBuPO3}4{μ3-OEt}]

The reactions of zinc alkyls with tert-butylphosphonic acid in 2 : 1 and 1 : 1 molar ratios afforded [[(ZnMe)(4-)(THF)2][tBuPO3]2] (2) and [[(ZnEt)3(Zn(THF))3][tBuPO3]4[mu3-OEt]] (3), respectively. Compounds 2 and 3 have been fully characterised by means of spectroscopic and analytical methods. Single-crystal X-ray diffraction studies revealed that zinc phosphonates 2 and 3 are tetra- and hexa-nuclear, respectively. This is in contrast to the dodecanuclear zinc phosphonate [[Zn2(THF)2(ZnEt)6Zn4(mu4-O)][(tBuPO3)8]] (1) obtained in a 1.5 : 1 reaction between zinc alkyls and tBuP(O)(OH)2.

Ab Initio Chemical Synthesis of Designer Metal Phosphate Frameworks at Ambient Conditions

Stepwise hierarchical and rational synthesis of porous zinc phosphate frameworks by predictable and directed assembly of easily isolable tetrameric zinc phosphate [Zn(dipp)(solv)]4 (dippH2 = diisopropylphenyldihydrogen phosphate; solv = CH3OH or dimethyl sulfoxide) with D4R (double-4-ring) topology has been achieved. The preformed and highly robust D4R secondary building unit can be coordinatively interconnected through a varied choice of bipyridine-based ditopic spacers L1-L7 to isolate eight functional zinc phosphate frameworks, [Zn4(dipp)4(L1)1.5(DMSO)]·4H2O (2), [Zn4(dipp)4(L2)1.5(CH3OH)] (3), [Zn4(dipp)4(L1)2] (4), [Zn4(dipp)4(L3)2] (5), [Zn4(dipp)4(L4)2] (6), [Zn4(dipp)4(L5)2] (7), [Zn4(dipp)4(L6)2] (8), and [Zn4(dipp)4(L7)2] (9), in good yield. The preparative procedures are simple and do not require high pressure or temperature. Surface area measurements of these framework solids show that the guest accessibility of the frameworks can be tuned by suitable modification of bipyridine spacers.

An efficient synthetic route to primary and secondary condensation products of silanetriols starting from (arylamino)trichlorosilanes

Stoichiometry dependent hydrolysis of (arylamino)-silyltrichlorides using anhydrous N2H4 as the HCl acceptor and dehydrating agent leads to the formation of the primary and secondary condensation products of silanetriols, tetrahydroxydisiloxanes [Ar(SiMe3)NSi(OH)2]2O and cyclotrihydroxytrisiloxanes [Ar(SiMe3)NSi(OH)O]3, respectively.

Molekulares Aluminophosphonat: isotype Modellverbindung für die sekundäre Doppel-6-Ring(D6R)-Baueinheit von Zeolithen

Bei richtiger Wahlder Grose der Substituenten an den Aluminium- und Phosphorbausteinen entsteht in der Reaktion von Alkylaluminiumverbindungen mit Phosphonsauren ein hexameres Aluminophosphonat ([MeAlO3PtBu]6). Der zentrale Kern, Al6O18P6 (siehe Bild), hat die Form einer zylindrischen Trommel, die an die Doppel-6-Ring-Baueinheit in Zeolithen erinnert.

Hydroxy-phenyl Zn(II) porphyrin self-assembled monolayer as a diffusion barrier for copper-low k interconnect technology

In this paper, we have studied the application of metallated porphyrin self-assembled monolayer (SAM) as a copper diffusion barrier for low-k inter-metal dielectric (IMD) CMOS technologies. SAM formed on hydrogen silesquioxane (HSQ), which is a low-k dielectric, has been demonstrated to be effective in preventing diffusion of copper ions into the porous dielectric. This has been shown by fabricating Cu-HSQ-Si and Cu-SAM-HSQ-Si metal-insulator-semiconductor test structures. Bias-temperature stress (BTS) studies have been done to investigate the effectiveness of SAM as a diffusion barrier. Formation of SAM on HSQ has been characterized using Fourier Transform Infra-red Spectroscopy studies. Thermogravimetric analysis (TGA) of hydroxyl-phenyl Zn(II) porphyrin has been used to verify thermal stability of the molecule under back-end-of-line (BEOL) process conditions.

Ruthenium-mediated selective cleavage of nitrogen–carbon bond of the diimine function. Synthesis, spectroscopic and redox properties of the complexes [Ru(L)2{−OC6H4C(CH3)NH}][ClO4] (L=2,2′-bipyridine and 1,10-phenanthroline) and the crystal structure of the bipyridine derivative

Abstract The reactions of Ru(bpy)2(CO3) (bpy=2,2′-bipyridine) and Ru(phen)2(CO3) (phen=1,10-phenanthroline) with the binucleating phenolato diimine function, OHC6H4C(CH3)NCH2C6H4CH2N(CH3)CC6H4OH, H2L in ethanol solvent under dinitrogen atmosphere result in ruthenium bipyridine/phenanthroline heterochelates [Ru(bpy)2/(phen)2L′](ClO4) 1 where L′ corresponds to the ketonic imine function −OC6H4C(CH3)NH incorporating the rare CNH fragment. In the course of the reaction the NC bond of the diimine function in H2L has been selectively cleaved. The formation of 1 has been authenticated by single-crystal X-ray structure of the bipyridine derivative (1a). The RuN5O coordination sphere is distorted octahedral. The diamagnetic complexes 1 exhibit 1:1 conductivity in acetonitrile solution. The complexes show strong RuII→π*(bpy)/(phen) MLCT transitions in the visible region and intra-ligand transitions in the UV region. The complexes exhibit moderately strong emissions near 700 nm from the lowest energy MLCT bands (Φ=1.7–2.2×10−2). The complexes (1a and 1b) display reversible ruthenium(III)–ruthenium(II) couple near 0.5 V, irreversible ruthenium(III)→ruthenium(IV) oxidation near 1.7 V and one ligand-based (L′) oxidation near 2.0 V versus SCE. The reductions of the bpy and phen ligands have been observed at the negative side of SCE. The electrochemically oxidized ruthenium(III) complexes (1a+ and 1b+) are found to be unstable at 298 K and exhibit rhombic EPR spectra having three distinct g values corresponding to the trivalent ruthenium(III) under distorted octahedral arrangement. The oxidized complexes (1a+ and 1b+) exhibit LMCT transitions near 750 nm.

SYNTHESIS AND CHARACTERIZATION OF NEW (CHLOR0)AMINOSILANES: X-RAY CRYSTAL STRUCTURE OF [(2,6-Me2C6H3NH)2SiCl2]

Abstract Starting from racemic α-methylbenzyl amine or α-methylbenzyl bromide, new (amino)trichlorosilanes (MePhC(H))(SiMe3)NSiCl3(1) and (MePhC(H))(2,6-Me2C6H3) NSiCl3 (2) have been synthesized in good yields. The products have been characterized by analytical and IR, mass, and NMR (1H and 29Si) spectroscopic techniques. The diamino-dichlorosilane (2,6-Me2C6H3NH)2SiCl2 (3) obtained as the side product during the synthesis of 2 has been characterized by a single crystal X-ray diffraction study.

Porphyrin induced changes in charge transport of graphene FET

The transport properties of back-gated graphene field effect transistors (GFETs) can be tuned via chemical doping. In this study, we report alteration of charge transport properties of GFET via 5-(4-hydroxyphenyl)-10,15,20-tri-(p-tolyl) zinc(II) porphyrin (Zn(II)-TTPOH) and its free base counterpart. We propose that, the porphyrin induces p-type doping in graphene.