Janarthanan Gopalakrishnan

Bio: Janarthanan Gopalakrishnan is an academic researcher from Papua New Guinea University of Technology. The author has contributed to research in topics: Coordination complex & Carbon-13 NMR. The author has an hindex of 3, co-authored 9 publications receiving 79 citations. Previous affiliations of Janarthanan Gopalakrishnan include Applied Science Private University.

Aminophosphines: their chemistry and role as ligands and synthons

Abstract: In recent years, research in organophosphorus chemistry has mainly focused in designing newer and better phosphorus ligands for synthesizing novel metal complexes with improved catalytic activities. Aminophosphines [tricoordinate phosphorus(III)–nitrogen systems] are considered as versatile compounds owing to the presence of nitrogen centres which, in principle, can influence additional reactivity features. They are quite sensitive to air and moisture due to the presence of polar PN bond(s). In spite of this, research in aminophosphine chemistry is gaining momentum day-by-day and this is due mainly to one reason: their rich behaviour as ligands in metal complex chemistry and subsequently in catalysis. Their role as synthons in inorganic heterocyclic chemistry has also helped produce new types of heterocycles. In this paper, the chemistry of simple acyclic aminophosphines (synthesis, characterization, reactivity and applications) is covered and particular focus is given to their ability to form chalcogenides along with their role played as ligands in coordination chemistry and as synthons in inorganic heterocyclic chemistry. Copyright © 2009 John Wiley & Sons, Ltd.

IR, Proton, and Carbon-13 NMR Spectral Characterization of Some Chiral and Achiral Aminophosphines and Their Selenides

Abstract: Though aminophosphines have been known for a century, and a large variety of such compounds has been synthesized for different aspects of their chemistry, until now, no examples are available on phosphines containing three different amino substituents. In this study, the first examples of such chiral tris(amino)phosphines and o-phenylenedioxo(amino)phosphines were successfully synthesized using condensation reactions, and they were converted to their respective selenides using a simple oxidative addition reaction. The compounds are characterized by IR, 1H, and 13C NMR spectral techniques, and the spectral aspects are presented. The spectral studies (i) indicated that they are indeed powerful tools for structural elucidation of compounds; (ii) showed the effect of heavier selenium atom on the P–N bond rotation process; and (iii) further supported the fact that dipolar structure predominates over the π-bond structure for the aminophosphine selenides. Supplemental materials are available for this article. Go...

Aminophosphines: Their Chemistry and Role as Ligands and Synthons

Abstract: In recent years, research in organophosphorus chemistry has mainly focused in designing newer and better phosphorus ligands for synthesizing novel metal complexes with improved catalytic activities. Aminophosphines [tricoordinate phosphorus(III)–nitrogen systems] are considered as versatile compounds owing to the presence of nitrogen centres which, in principle, can influence additional reactivity features. They are quite sensitive to air and moisture due to the presence of polar PN bond(s). In spite of this, research in aminophosphine chemistry is gaining momentum day-by-day and this is due mainly to one reason: their rich behaviour as ligands in metal complex chemistry and subsequently in catalysis. Their role as synthons in inorganic heterocyclic chemistry has also helped produce new types of heterocycles. In this paper, the chemistry of simple acyclic aminophosphines (synthesis, characterization, reactivity and applications) is covered and particular focus is given to their ability to form chalcogenides along with their role played as ligands in coordination chemistry and as synthons in inorganic heterocyclic chemistry. Copyright © 2009 John Wiley & Sons, Ltd.

Analysis of ash suspension obtained from Piper aduncum that claimed to cure cancer in Papua New Guinea

Abstract: People all around the world have learnt to effectively use the natural resources around them to improve the quality of lives, for example, adaptation of folk medicine and traditional healing through ethnobotanical or ethnomedicinal uses of medicinal plants and herbs[1]. A numerous book volumes, research reports and articles on plants and their medicinal values are available. Papua New Guinea (PNG) is a small island country in the Oceania continent with an approximate population of 7.5 millions, geographically having huge mountainous terrains and shares the border with Indonesia. PNG, prosperous in flora and fauna varieties, is culturally very rich with numerous traditional habits that are still being practiced and followed on a routine basis. Piper aduncum (P. aduncum), commonly known as spiked pepper, is shade-intolerant specie and is one amongst the thousand varieties in the shrub class of the Piperaceae family[2]. It was introduced to the PNG community from the South America, and it has invasive nature as well as the ability to make the drying rate of the soil faster. Indeed there were some concerns because of its interference with agriculture[3] , which resulted in serious impact on the economic, ecological, sociological, nutrient and botanical welfare in PNG[4], mainly because of the loss of primary forest with the replacement of indigenous vegetations. Barring these historical events that are still debatable for their pros and corns, the shrub now occupies most of the places in and around the Bulolo region of Morobe Province of PNG. In addition, it is very commonly found in Hawaii, Fiji, Vanuatu, Solomon Islands, Boreno, Mexico, Central America, Suriname, Cuba, Trinidad and Tobago, Jamaica and Costa Rica[3].

A Deep Analysis on Widely Used Condensation Route for Preparing Aminophosphines: Synthesis and Spectral Characterization of an Aminobis(chlorophosphine), (NC4H8N)[P(i-Pr2N)Cl]2

Abstract: Aminophosphines are useful as ligands and the most convenient method to synthesize is the condensation route that is straightforward, simple and easy to execute and get the products. RxPClz (x = 0–2, y = 1–3) and amines are widely used as phosphorus and nitrogen substrates. Vast examples such as Phx(R2N)yPClz [x 0; z < 3] are available in the literature which used condensation route. A deep analysis was carried out on this route and the author analyzes various parameters that affect product formation, purity, and yield. Using the optimized conditions, (NC4H8N)[P(i-Pr2N)Cl]2 was prepared and spectrally characterized.

Aminophosphines: A Double Role in the Synthesis of Colloidal Indium Phosphide Quantum Dots

Abstract: Aminophosphines have recently emerged as economical, easy-to-implement precursors for making InP nanocrystals, which stand out as alternative Cd-free quantum dots for optoelectronic applications. Here, we present a complete investigation of the chemical reactions leading to InP formation starting from InCl3 and tris(dialkylamino)phosphines. Using nuclear magnetic resonance (NMR) spectroscopy and single crystal X-ray diffraction, we demonstrate that injection of the aminophosphine in the reaction mixture is followed by a transamination with oleylamine, the solvent of the reaction. In addition, mass spectrometry and NMR indicate that the formation of InP concurs with that of tetra(oleylamino)phosphonium chloride. The chemical yield of the InP formation agrees with this 4 P(+III) → P(−III) + 3 P(+V) disproportionation reaction occurring, since full conversion of the In precursor was only attained for a 4:1 P/In ratio. Hence it underlines the double role of the aminophosphine as both precursor and reducing ag...

Intramolecular Hydroamination of Unbiased and Functionalized Primary Aminoalkenes Catalyzed by a Rhodium Aminophosphine Complex

Abstract: We report a rhodium catalyst that exhibits high reactivity for the hydroamination of primary aminoalkenes that are unbiased toward cyclization and that possess functional groups incompatible with more electrophilic hydroamination catalysts. The rhodium catalyst contains an unusual diaminophosphine ligand (L1) that binds to rhodium in a κ3-P,O,P mode. The reactions catalyzed by this complex typically proceed at mild temperatures (room temperature to 70 °C) and occur with primary aminoalkenes lacking substituents on the alkyl chain that bias the system toward cyclization, with primary aminoalkenes containing chloride, ester, ether, enolizable ketone, nitrile, and unprotected alcohol functionality, and with primary aminoalkenes containing internal olefins. Mechanistic data imply that these reactions occur with a turnover-limiting step that is different from that of reactions catalyzed by late-transition-metal complexes of Pd, Pt, and Ir. This change in the turnover-limiting step and resulting high activity o...

Mechanistic Insight and Optimization of InP Nanocrystals Synthesized with Aminophosphines

Abstract: We study the synthesis of indium phosphide quantum dots using InCl3, tris(dimethylamino)phosphine (P(NMe2)3), and oleylamine. We optimized the reaction conditions to reach high chemical yield (∼70%) and size control of the quantum dots with absorption maxima over all the visible range. Kinetic studies of the formation of the quantum dots show that, under certain conditions, the growth of nanoparticles seems to approach a LaMer type growth. We have used 31P NMR, mass spectroscopy, and DFT calculations to decipher the reaction mechanisms of InP formation at the molecular level. The mechanistic investigation is in good agreement with the conclusions drawn from the optimization of the synthetic conditions.

Functional Short-Bite Ligands: Synthesis, Coordination Chemistry, and Applications of N-Functionalized Bis(diaryl/dialkylphosphino)amine-type Ligands.

Abstract: The aim of this review is to highlight how the diversity generated by N-substitution in the well-known short-bite ligand bis(diphenylphosphino)amine (DPPA) allows a fine-tuning of the ligand properties and offers a considerable scope for tailoring the properties and applications of their corresponding metal complexes. The various N-substituents include nitrogen-, oxygen-, phosphorus-, sulfur-, halogen-, and silicon-based functionalities and directly N-bound metals. Multiple DPPA-type ligands linked through an organic spacer and N-functionalized DRPA-type ligands, in which the PPh2 substituents are replaced by PR2 (R = alkyl, benzyl) groups, are also discussed. Owing to the considerable diversity of N-functionalized DPPA-type ligands available, the applications of their mono- and polynuclear metal complexes are very diverse and range from homogeneous catalysis with well-defined or in situ generated (pre)catalysts to heterogeneous catalysis and materials science. In particular, sustained interest for DPPA-t...

A very peculiar family of N-heterocyclic phosphines: unusual structures and the unique reactivity of 1,3,2-diazaphospholenes

Abstract: This Perspective gives an account of the peculiar electronic and molecular structures of N-heterocyclic phosphines featuring either a single 1,3,2-diazaphospholene (DAP) ring with an exocyclic P-substituent X or two DAP rings linked by a P–P bond (bis-diazaphospholenyls), respectively, and their impact on the chemical properties of these molecules. The bonding situation in simple DAPs is epitomized by strong hyperconjugation between endocyclic π-type electrons and the exocyclic P–X bond. This interaction may induce a perceptible ionic polarization of the P–X bond which can persist even in the limit of a vanishing electronegativity gradient between P and X, and becomes visible in unusual geometric distortions of molecular structures and a unique chemical behaviour. Structural distortions are particularly evident in bond lengthening effects in P-halogen and P-phosphino derivatives R2P–DAP (with R2P ≠ DAP) which span the whole range from covalent molecules to contact ion pairs with a close relation to frustrated Lewis-pairs. The most significant impact on the chemical properties is found for P-phosphino- and P-hydrogen derivatives where reactions at substantially accelerated rates or totally new reaction modes can be observed, and new stoichiometric and first catalytic processes exploiting these features are currently emerging. The recently discovered bis-diazaphospholenyls differ from the simple derivatives as their central bond remains unpolarised as a consequence of the symmetric molecular structure. The occurrence of low-energy P–P bond homolysis that was nonetheless observed in one case is according to the results of thermochemical studies of P–P bond fission reactions attributable to the effects of steric congestion and induces chemical reactivity that can be considered complementary to that of the simple R2P–DAPs. Some concluding remarks will pay attention to a facet of DAP reactivity that has so far been widely neglected but is currently receiving increasing attention, namely well-defined ring-opening processes.