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Research Interests

Inorganic Materials & Supramolecular Chemistry

(A) Nanoscale Materials: The study of nanometer size compounds is an exciting area of research which offers opportunities for innovation and creativity. Nanoscale materials exhibit quantum behavior due to their size and are promising materials for new technologies. Our research focuses on the synthesis of nanoscale metal chalcogenide materials and the characterization of their properties. The chemical, physical, electronic, optical, magnetic and catalytic properties of nanocrystals depend on the size and shape of the nanomaterials. However synthesis of stable monodispersed nanocrystals is a real challenge in nanoscience. Currently we are interested in developing solar energy cells. Single-source precursor Chemistry: We have been interested in developing the chemistry of transition and main group metal compounds with chalcogen containing ligands, RC{O}E-, RE-, R2NCS2 = (where E = S, Se and Te), dithioacetylacetonato and related ligands. We have shown that many of these compounds can be used as precursors to metal chalcogenides (as amorphous or crystalline powders, films and nanoparticles). Currently we are interested in the Group 6, 11, 12, 13, 14, transition and lanthanide metals. We have also developed single precursor routes to synthesize highly monodispersed nanoparticles of ME (M = Zn, Cd & Hg), M2E (M = Cu & Ag), M2E3 (M = As, Sb & Bi), AME2 (A = Cu, Ag; M = Ga & In), where E = S, Se & Te, etc..   (a)   (b) Figures: (a) The formation of different size and shapes of Ag2Se nanocrystals from the precursor [(Ph3P)Ag2 (SeC{O}Ph)2]. (b) The toluene-soluble AgInS2 obtained from [(Ph3P)2AgIn(SeC{O}Ph)4] exhibits NLO properties. Oxide Materials: Oxide Materials: A wide range of materials have been considered as energy storage materials; of these Li ion battery is a promising one and of late this is one of the hottest areas of research due to recent oil crisis. We entered this field by accident when reported single-molecular precursor route to LiMO2 battery materials. The compounds [Li(H2O)M(N2H3CO2)3].H2O (M = Ni, Co) on pyrolysis yield LiNiO2 and LiCoO2 at 700oC in oxygen atmosphere and at T > 700oC in air. Currently we are collaborating with Physics and Chemical Engineering colleagues in developing LiFePO4 battery materials. We synthesized LiFePO4 nanoplates with uniform coating of 5 nm thick amorphous carbon layer by solvothermal method. The thickness along b-axis is found to be 30-40 nm, and such morphology favors a shorter diffusion length for Li+ ions, while exterior conductive carbon decoration provides connectivity for facile electron diffusion, resulting in high rate performances close to theoretical value, shown below. We also filed a US Patent on this material. Figures: (Left) Galvanostatic charge - discharge cycle curves for LiFePO4C and (right) Capacity vs. Cycle number plots of LiFePO4/C nanoplates at various current rates 0.1 to 30 C (B) Crystal Engineering: Current research in our group includes rational design of metal coordination polymers with multi-dimensional network structures using a number of linear and angular spacer ligands. In this exploratory research we systematically study the properties of supramolecular building blocks such as shape, size and directionality of the functional groups to understand how these parameters control and influence the crystal packing and hence the supramolecular structures. Our interests include supramolecule-based magnets and porous materials for gas storage properties. Some of the current topics are given below. Topochemical photodimerization Reactions: Polymerization by photo-crosslinking is one of the most versatile technologies for producing organic polymers. On the other hand, it is challenging to stack and crosslink the C=C bonds in metal coordination polymers by solid-state photochemical [2+2] cycloaddition reactions. We utilize various crystal engineering tools to achieve this endeavor.   (a)   (b)   (c)   (d)   Figures: (a) he solid-state supramolecular structural transformation of a ladder-like coordination polymer to another by [2+2] photodimerization reaction. (b) Formation hydrogen bonded helical water stream inside a helical staircase coordination polymer. (c) Structural transformation between elusive cyclic water heptamer and bicyclic (H2O)7 accompanied by phase transition. (d) Water helicate hosted in the crystal lattice. Some of the topics we are currently interested in the crystal engineering area are as follows. a) Solid-state Supramolecular Structural Transformations b) Water Clusters c) pH Dependent Supramolecular Transformations in solution d) Solid-State Photochemistry of Metal Complexes and Coordination Polymers e) Porous coordination network structures as energy storage materials f) Coordination polymeric gels, fibers, films, etc. Cover pages Front Cover, 2005 Back Cover, 2006 Front Cover, 2006 Front Cover, 2006 Inside Cover, 2007 Front Cover, 2008 Inside cover, 2008 Front cover, 2008 Inside Cover, 2009 Book cover 2006 IUCr Newsletter, 2006

Representative Publications

Over 380 publications yielded h-Index: 38 and average citation of 17.37

1. E.R.T. Tiekink and J.J. Vittal (Book Editors), Frontiers in Crystal Engineering, ISBN: 0-470-02258-2, Wiley, 2006.
2. J.J. Vittal and M.T. Ng, "Chemistry of Metal Thio- and Selenocarboxylates - Precursors for Metal Sulfide/Selenide Materials", Thin Films and Nanocrystals, Acc. Chem. Res., 39 (2006) 869. (invited review and cover page & one of the most-accessed articles in October-November, 2006).
3. M. Nagarathinam and J.J. Vittal, "A rational approach to cross-linking of coordination polymers by photochemical [2+2] cycloaddition reaction", Macromol. Rapid Commun., 27 (2006) 1091. (invited feature article & back cover page).
4. J.J. Vittal, "Supramolecular structural transformations involving coordination polymers in the solid state", Coord. Chem. Rev. 251 (2007), 1781. (invited review) (Highly cited paper by Thomson's Essential Science Indicators)
5. R. Ganguly, B. Sreenivasulu and J.J. Vittal,"Amino acid containing reduced Schiff base as the building blocks for supramolecular structures" Coord. Chem. Revs. 252(8-9) (2008) 1027-1050 (invited & one of the top 25 hottest articles, April-June, 2008 )
   
6. M. H. Mir, L. Wang, M. W. Wong and J. J. Vittal, ‘Water Helicate, (H2O)7 Hosted by Diamondoid Metal–Organic Framework,’ Chem. Comm., (30) (2009) 4539-4541
7. M. Nagarathinam, A.M.P. Peedikakkal and J.J. Vittal, "Stacking of double bonds for photochemical [2+2] cycloaddition reactions in the solid-state" Chem. Commun., (42) (2008) 5277 (invited feature article)
8. W. L. Leong, A. Y.-Y. Tam, S. K. Batabyal, L. W. Koh, S. Kasapis, V.W.-W. Yam, and J.J. Vittal, "Fluorescence Enhancement of Coordination Polymeric Gel", Chem. Commun., (2008) 3628-3630 (inside cover page)
9. W.L. Leong, S.K. Batabyal, S. Kasapis and J.J. Vittal, "Fluorescent Magnesium(II) Coordination Polymeric Hydrogel", Chem.- A Eur. J., 14(29) (2008) 8822 (cover page)
10. M. Nagarathinam and J.J. Vittal, 'Photochemical [2+2] cycloaddition as a tool to study solid state structural transformation,' Chem. Commun., (2008) 438 (back-to-back issues & amongst the top 10 most accessed article from the online version in January 2008)
11. A.M.P. Peedikakkal and J.J. Vittal, 'Photodimerization of 1D hydrogen-bonded zwitter-ionic lead(II) complex and its isomerization in solution,' Chem. Commun., (2008) 441 (back-to-back issues and cover page)
12. M.H. Mir & J.J. Vittal, "Phase Transition Accompanied by Transformation of an Elusive Discrete Cyclic Water Heptamer to a Bicyclic (H₂O)₇ Cluster", Angew. Chem. Int. Ed., 46 (2007) 5925-5928
13. L. Tian, H.I. Lim, W. Ji, J.J. Vittal, "One pot synthesis and third-order nonlinear optical properties of AgInS₂ nanocrystals", Chem. Commun., (2006) 4276. (cover page).
14. M. Nagarathinam and J.J. Vittal, "Anisotropic movements of coordination polymers upon desolvation: Solid-state transformation of linear 1D coordination polymer to ladder-like structure", Angew. Chem. Int. Ed., 45 (2006) 4337.
15. M.T. Ng, C.B. Boothroyd and J.J. Vittal, "One-pot synthesis of new phase AgInSe₂ nanorods", J. Am. Chem. Soc., 128 (2006) 1178.
16. M.T. Ng, C. Boothroyd and J.J. Vittal, "Shape and size control of Ag₂Se nanocrystals from single precursor [(Ph₃P)₃Ag₂ (SeC{O}Ph)₂]", Chem. Commun., (2005) 3820. (hot article).
17. N.L. Toh, M. Nagarathinam and J.J. Vittal, "Topochemical photodimerization in the molecular ladder metal coordination polymer [{(CF₃CO₂)(m-O₂CCH₃)Zn}₂(m-bpe)₂]n (where bpe = 4,4'-bipyridylethelene) via single-crystal to single-crystal transformation", Angew. Chem. Int. Ed., 44 (2005) 2237. (cover page).
18. B. Sreenivasulu and J.J. Vittal, "Helix inside a helix: Encapsulation of Hydrogen-bonded Water Molecules inside a Staircase Coordination Polymer", Angew. Chem. Int. Ed., 43 (2004) 5769. (Highly cited paper by Thomson's Essential Science Indicators)
19. M.T. Ng, T.C. Deivaraj, W.T. Klooster, G.J. McIntyre and J.J. Vittal, 'Hydrogen-bonded Polyrotaxane-like structure containing cyclic (H₂O)₄ in [Zn(OAc)₂(m-bpe)]x₂H₂O: X-Ray and Neutron Diffraction Studies', Chem. Eur. J., 10 (2004) 5853.
20. C.-T. Yang, M. Vetrichelvan, X. Yang, B. Moubaraki, K. S. Murray and J. J. Vittal, 'Syntheses, structural properties and catecholase activity of copper(II) complexes with reduced Schiff base N-(2-hydroxybenzyl)-amino acids', Dalton Trans., (2004) 113-121.(Amongst the top 10 most accessed article through web in Dec. 2003).
21. M. Lin, K.P. Loh, T.C. Deivaraj and J.J. Vittal, 'Heterogeneous reaction route to CuInS₂ thin films', Chem. Commun., (2002) 1400.
22. T.C. Deivaraj, J.H. Park, M. Afzaal, P. O'Brien and J.J. Vittal. 'Single source precursors to ternary silver indium sulfide materials', Chem. Commun., (2001) 2304.
23. C.P. McArdle, J.J. Vittal and R.J. Puddephatt, Molecular topology:Easy self-assembly of an organometallic doubly braided[2]-Catenane, Angew. Chem. Int. Ed.., 39 (2000) 3819.
24. J.D. Ranford, J.J. Vittal, D. Wu and X. Yang,' Thermal Conversion of a Helical Coil to a 3-D Chiral Framework', Angew. Chem. Int. Ed., 38 (1999) 3498.
25. J.D. Ranford, J.J. Vittal and D. Wu, 'Topochemical Conversion of Hydrogen Bonding to Covalent Three Dimensional Networks,' Angew. Chem. Int. Ed., 37 (1998) 1114. (highlighted in Angew. Chem. Int. Ed., 38 (1998) 1211).