Author Profile

Arunachalam Ramanan

Born: Veppathur, Tamil Nadu, India Ph.D. : Indian Institute of Science (IISc) Bangalore (1984). Post Doctoral Fellow : IISc Bangalore (1984-1985) University of Exeter, UK (1986-1989) Binghamton University, New York, USA (1989-1990). Visiting Faculty: Binghamton University, New York, USA (2005-2006). Professor at Indian Institute of Technology Delhi, 1990-present.

Recent Posts


Role of Hydrogen-Bonded Interactions in the Crystal Packing of Phenylenediammonium Phosphomolybdates

Self-assembled synthesis of three new organic/inorganic hybrid solids (1−3) in the presence of isomeric phenylenediammonium ions (p-, m-, and o-) demonstrates the role of nonbonding interactions in the construction of phosphomolybdate-based solid-state assemblies. In 1, crystal packing is dominated by two kinds of supramolecular assemblies:  an unusual pentadecameric water cluster linked through p-phenylenediammonium (ppda) cations and a hydrogen-bonded assembly of a ppda cation with four phosphomolybdate anions. In 2, a pair of m-phenylenediammonium (mpda) cations linked through π···π interactions envelops a phosphomolybdate anion from either side through hydrogen bonding mediated by water molecules forming butterfly-like supramolecular motifs. In 3, a new kind of O−W−O−W (organic−water) linker formed by alternate hydrogen bonding between o-phenylenediammonium (opda) and water molecules; such motifs are well decorated around a pentamolybdate cluster anion leading to the formation of the three-dimensional architecture. Crystal structures of 1−3 reveal that supramolecular synthons earlier observed between water and organic ammonium cations in the presence of octamolybdate anions are broken in the presence of diphosphopentamolybdates due to the latter anion’s strong affinity for hydrogen bonding with the cations.


Structure-Directing Role of Hydrogen-Bonded Dimers of Phenylenediammonium Cations:  Supramolecular Assemblies of Octamolybdate-Based Organic−Inorganic Hybrids

Crystallization of three new organic/inorganic hybrid solids (1−3) based on octamolybdate under self-assembly conditions has demonstrated the structure-directing role of three hydrogen-bonded organic dimers (supramolecular synthons) in the construction of multidimensional networks. In acidified aqueous molybdate solution, isomeric phenylenediammonium ions form dimers through strong hydrogen-bonding and/or π−π interactions, which in turn dictate the supramolecular assemblies between themselves or with octamolybdate anions that eventually result in the growth of hybrid solids.