Poster Session 2

5:15 - 6:15 PM

Poster Presentation LINK

Rh(III)-catalyzed redox-neutral chemo-divergent coupling of N-phenoxyacetamides and alkylidenecyclopropanes (ACPs) has been documented. Reaction proceeds via C-H activation, stereoselective beta-carbon elimination followed by beta-hydride elimination resulting in o-dienylation of phenols in nonpolar solvents. Whereas, [3+2]-annulation leading to dihydrobenzofu-rans was realized in polar fluorinated solvents. It was observed that the nucleophilic directing group controls the elimination of beta-carbon and so plays a vital role for achieving high stereoselectivities. Synthetic utility of the dienylation and annulation was demonstrated by carrying out gram scale reaction and further derivatization.

Poster Presentation LINK

Is Lanthanide-Transition Metal Direct Bond a Route to Achieving New Generation {3d-4f} SMMs?

Lanthanide based Single-Molecule Magnets are gaining wide attention due to their potential application in emerging technologies. One of the main challenges in this area is quenching quantum tunnelling of magnetisation (QTM), which often undercut the magnetisation reversal barrier. Among several strategies employed, enhancing the exchange coupling has been studied in detail, with large exchange yielding strong quenching of QTM effects. Lanthanides, however, suffer from weak exchange offered by the deeply buried 4f orbitals and numerous attempts to enhance exchange coupling in {3d-4f} pairs has not crossed value larger than 30 cm-1. In this work, using a combination of DFT and ab initio CASSCF/RASSI-SO method, we have explored Lanthanide-transition metal direct bond as a tool to quench QTM effects. In this direction, we have modelled [PyCp2LnMCp(CO)2] (Ln= Gd(III), Dy(III), Er(III) and M=V(0), Mn(0), Co(0) and Fe(I) and here PyCp2=2,6- (CH2C5H3)2C5H3N]2- using [PyCp2DyFeCp(CO)2] example reported by Nippe et al. (C. P. Burns, X. Yang, J. D. Wofford, N. S. Bhuvanesh, M. B. Hall and M. Nippe, Angew.Chem.Int. Ed. 2018, 57, 8144). Bonding analysis reveals a dative Ln–TM bond with a donation of (V/Mndxy-*CO) to 5dz2 (Gd) in the case of Gd-V and Gd-Mn and 4s(Co) to 5dxy/5dyz (Gd) for Gd-Co with transition metal ion found to be in low-spin S = ½ configurations in all cases. B3LYP/TZV (Gd;CSDZ) calculations on [PyCp2GdMCp(CO)2] yield JGd-V= -46.1 cm-1, JGd-Mn = -57.1, JGd-Co= +55.3 cm-1, JGd-Fe+= +13.9 cm-1, JGd-Vhs= -162.1 cm-1 and JGd-Mnhs= -343.9 cm-1 and unveiling record-high J values for {3d-4f} complexes. Mechanism of magnetic coupling is developed, which discloses the presence of strong 3d-4f orbital overlap dominating in most cases studied, leading to antiferromagnetic exchange. When these overlaps are weaker and 3d to Gd(5dz2), charge transfer dominates, yielding a ferromagnetic coupling for Gd-Co/Gd-Fe+ complexes. Calculations performed on the anisotropic Dy(III) and Er(III) complexes reveal that the ground state gzz axis lies along the Cp-Ln-Cp axis and the Ln–TM bonds, respectively. Thus the Ln–TM bond hinder the single-ion anisotropy of the Dy(III) case by offering equatorial ligation and bringing the mJ = ± ½ state lower in energy, and at the same time, it helps enhance the axiality for the Er(III) case. When the strong {3d-4f} exchange couplings are introduced, record-high barrier heights as high as 229 cm-1 were accomplished. Furthermore, the exchange coupling annihilates the QTM effects and suggests Lanthanide-transition metal direct bond as a viable alternative to enhance exchange coupling to bring {3d-4f} complexes back in the race for high-blocking SMMs.

Poster Presentation LINK

Metalloenzymes are most abundant in living organisms. Their remarkable catalytic activity typically comes from the first coordination sphere of the transition metal-based cofactors. The amino acid residues at the closest vicinity of the cofactor, constructs the second coordination sphere which plays the key role in controlling the substrate specificity during the catalysis. Scientists have harnessed the unmatched catalytic efficacy of natural metalloenzymes towards unnatural organic transformations via genetic modification of the host proteins. In this context, artificial metalloenzymes (ArMs) further broadens the scope of metalloenzyme catalysis for abiological reactions. In this context, artificial metalloenzymes (ArMs) further broadens the scope of metalloenzyme catalysis for abiological reactions. In their pioneering work, Wilson and Whiteside demonstrated the construction of ArMs by simply exploiting the strong noncovalent interaction between biotin and strept(avidin). Later, Ward group has heightened the applicability of biotin-strept(avidin) based ArMs towards diverse asymmetric organic syntheses. The main advantage of using strept(avidin) as the host protein is their high thermostability and well tolerance towards extreme pH, denaturing agents and extensive mutations. Additionally, anchoring of the large biotinylated metal complexes inside those proteins does not affect the protein stability and provides sufficient space for the interaction between substrates and metal cofactor inside the catalytic pocket. In this context, considering the potential of ArMs in stereo selectively catalyzing unnatural reactions, I will discuss the exploration of the catalytic efficacy of streptavidin-based ArMs towards CH bond functionalization via metal carbene migratory insertion.

Process Intensification Through Continuous Flow Chemistry

Poster Presentation LINK

The reactors used for the chemical synthesis are of two types viz; batch reactors and flow reactors. In the batch process, the concentration of reactant and product changes with time. But in the continuous flow process, the concentration of reactants and products remains constant with time at a given position of the tubular reactor. Continuous flow systems offer various advantages over traditional batch systems, such as ease of automation, integration of online analytics, superior mixing, and access to a higher range of temperatures and pressures.

In this poster, I’ll be briefing about how the Continuous Flow Process has helped in Intensifying the process, which will be helpful at the Industrial chemical synthesis. A comparative study of Batch Vs. Flow is done, and the advantages of the continuous flow process over the traditional batch process are highlighted.

Tellurium Containing Porphyrinoids

Poster Presentation LINK

Telluraporphyrinoids containing telluorophene ring(s) in the place of one or more pyrrole rings are most attractive hetero porphyrinoids because of their unusual and unique characteristics, which are quite different from other heteroporphyrinoids containing thiophene/furan/selenophene rings in place of pyrrole rings of porphyrinoids. 1 The physico-chemical properties of heteroporphyrinoids containing lighter chalconoids such as oxygen,sulfur and selenium exhibit similarity with each other but different from regular porphyrinoids and their chemistry is well established in literature. On the other hand, telluraporphyrinoids show unusual properties in terms of structure and reactivity compared to the other chalcogen containing porphyrinoids. This is ascribed to larger size of tellurium atom in comparison with oxygen, sulfur and selenium atoms which reduces the cavity size of porphyrinoid leading to stronger interactions among the inner core atoms of the

porphyrinoids and changes their structure and reactivity. For example, the telluraporphyrins have proven to be active catalysts in the bromination reactions of 4-pentenoic acid and 1,3,5-trimethoxybenzene which is ascribed to the ease of oxidation of core tellurium and consequent stabilization of the telluronium cation by the trans atom. The telluroporphyrinoids are very air-sensitive and have a tendency to extrude from telluorophene ring of porphyrinoid. A perusal of literature reveals that the tellurophene containing porphyrinoids relatively less explored as compared to other heteroporphyrinoids which may be due to lack of easily accessible stable telluorophene based precursors and high reactivity of telluroporphyrinoids. Specially, there are very few reports available on tellurophene containing expanded porphyrinoids to understand their physico-chemical and coordination properties

Regioselective Synthesis of Oxazepines, Benzo[a]carbazoles and Benzo[j]phenanthridine-diones by One-pot Hauser-Kraus Annulation and a Cascade of Ring Opening, Ring Expansion and Ring Contraction Reactions

Poster Presentation LINK

The oxazepines, carbazoles and benzophenanthridine-diones are found in various natural products and also known to possess various drug properties against mental illness, cancer and tuberculosis (TB). Therefore, the synthesis of these nitrogen containing heterocycles are in great demand. The synthesis of most of these heterocyclic compounds arises through multiple steps in low to moderate yields. Herein, we describe the one-pot regioselective synthesis of benzo[d]naphtho-oxazepines, benzo[a]carbazoles and benzo[j]phenathridine-diones by the reaction of 3-olefinic oxindoles with 3-nucleophilic phthalides. This cascade approach follows the four stage sequence of regioselective Hauser-Kraus (H-K) annulation, and a cascade of ring opening, ring expansion followed by de-carboxylative ring contraction reactions. The mechanism of the reaction is explained through experimental evidence by isolating the all stable intermediates, which revealed that the transformation involves four distinguishable stages. The current synthetic strategy induces new chemical entities for biological studies against cancer, TB and mental illness.

4-Pentyl-biphenyl-4'-carboxylic acid coated liquid crystal droplets for protein sensing application

Poster Presentation LINK

Sensing and characterization of a specific protein is the basis for the diagnosis of many diseases, molecular screening of toxins in food, and narcotics in blood. Liquid crystal (LCs) droplets prepared in an aqueous medium have been shown potential in detecting and sensing proteins at the LC aqueous interface. Proteins from the aqueous phase adsorbs at the LC/water interface decorated with secondary nonmesogenic molecules such as surfactant, lipids, polyelectrolytes, lead to change in the orientational order of LC droplets.^1-2 Development of LC droplets-based protein detection and sensing without preabsorbed molecules at the LC/water interface is essential for the fabrication of low-cost optical biosensors. Here we show our preliminary observation towards developing label-free detection of proteins (myoglobin, bovine serum albumin, and chymotrypsin) using nematic LC droplets. Doping of neat 4-cyano-4^/-pentyl biphenyl nematic LC with similar structure molecule 4-Pentyl-biphenyl-4^/-carboxylic (PBC) acid provides a platform for detection of native proteins. Mixing of proteins with preformed PBC doped LC droplets shows a change from radial to bipolar defect configuration transition. In my poster, I will present the methodology for the preparation and characterization of PBC decorated LC droplets to detect proteins, sensitivity towards the secondary structure of proteins.

Magnetic Behavior of Mononuclear Dihalo-Co(II) Carbazolylphosphine Oxide Complexes

Poster Presentation LINK

Research in the field of magnetism has attracted attention in the past and continues to be an active area in the present as well after the findings of magnetism at the molecular level. Materials which can retain their magnetization at molecular level just like bulk magnets are called single molecular magnets (SMM). These materials exhibit promising applications in high-density information storage, molecular spintronics, and quantum computing. Monometallic complexes based on 3d transition metal ions can exhibit appreciably enhanced magnetic anisotropy due to stabilization of an unquenched orbital moment. Understanding and controlling magnetic anisotropy at the level of a single metal ion is vital if the miniaturization of data storage is to evolve into transformative technologies. In this regard, three novel mononuclear tetrahedral cobalt(II) complexes [Co(L)2X2] where L= (9H-carbazol-9-yl)diphenylphosphine oxide) and X = I, Br, and Cl have been synthesized using a rationally designed synthetic approach, with the aim of acquiring single ion magnetic behavior. A detailed study of the variation in the dynamic magnetic properties of the Co(II) ion in tetrahedral ligand field has been carried out by changing the halide ligand (X = I(1), Br(2), Cl(3)). Field swift data shows the maximum SMM behavior for iodide complex 3. Further the incorporation of carbazole moiety in the ligand system opens up the possibility of photoinduced magnetism.