Ajay Kumar Jana

Assembling Porphyrins into Extended Network Structures by Employing Aromatic Dicarboxylates: Synthesis, Metal Exchange, and Heterogeneous Catalytic Studies

Three new metal-organic porphyrinic framework compounds of zinc and 5,10,15,20-tetrakis(4-pyridyl)porphyrin (TPyP) have been synthesized under solvothermal conditions. The compounds [Zn5 (C40 H24 N8 )(C8 H4 O4 )2 (NO3 )6 (DMA)2 ] (DMA)3 (H2 O)8 (1; DMA=dimethylacetamide), [Zn3 (C40 H24 N8 )(C8 H4 O4 )2 (DMF)](DMF)5 (H2 O)12 (2), and [Zn3 (C40 H24 N8 )(C12 H6 O4 )2 (DMA)2 ](H2 O)7 (3) have two (1) and three dimensionally (2 and 3) extended structures. All the three structures contain porphyrinic units connected through the carboxylate linkers. The nitrates bind the metal centers and are not hydrogen bonded. The different binding modes of nitrate in the structure of 1 are observed for the first time in a porphyrin-based MOF. The openness of the structure allowed us to explore metal exchange through a room-temperature metathetic route. Compound 2 undergoes 100 % exchange with copper, whereas compound 3 exchanges 70 % with copper. The copper-exchanged compounds Cu∈2 and Cu∈3 were observed to be good heterogeneous catalysts for many important organic reactions. The chemo and regioselective enamination of β-ketoesters, preparation of propargylamine derivatives as well as regioselective cycloadditions of alkyne and azide (click reactions) have been carried out with good yields and selectivity. All the compounds have been characterized by PXRD, IR, UV/Vis, atomic absorption spectroscopy (AAS), and energy-dispersive X-ray spectroscopy (for Cu exchange).

Novel amine templated three-dimensional zinc-organophosphonates with variable pore-openings

Five new amine-templated zinc-organophosphonate compounds have been synthesized hydrothermally in the presence of zinc, 1-hydroxyethane-1,1-diphosphonic acid (H4hedp) as the diphosphonate ligand and different aliphatic amines. All the five compounds have three-dimensional open-framework structures, which are formed by the connectivity between zinc ions and diphosphonate ligands, and the biprotonated amines are present inside the open-channels. Five different amines, namely ethylenediamine (EDA), diethylenetriamine (DETA), 1,2-diaminopropane (1,2-DAP), 1,3-diaminopropane (1,3-DAP) and diazobicyclooctane (DABCO), have been used to obtain three different classes of framework structures, and such types of amine-templated frameworks are observed for the first time in the family of organophosphonates. Compound I, [C2N2H10][Zn3(hedp)2]·H2O, and compound II, [C4N3H15][Zn3(hedp)2], have similar framework structures, though these compounds have been synthesized in the presence of EDA and DETA, respectively. Compound III, [C3N2H12][Zn3(hedp)2], and compound IV, [C3N2H12][Zn3(hedp)2], have the same molecular formula and framework structures; however, their amines are different, i.e. 1,2-DAP and 1,3-DAP, respectively. Compound V, [C6N2H14][Zn3(hedp)2], forms a different three-dimensional framework from the above structures in the presence of DABCO. By varying the amine molecules from EDA to 1,2-DAP or DABCO, the ring size can be tuned from 4-, 5-, 6-, and 8-membered to only 6-, and 8-membered. All the compounds have also been characterized by powder XRD, IR spectroscopy, and TGA. The luminescence properties of compounds I–V have also been studied.

Encapsulation of Silver Nanoparticles in an Amine-Functionalized Porphyrin Metal-Organic Framework and Its Use as a Heterogeneous Catalyst for CO2 Fixation under Atmospheric Pressure

A new porphyrin-based compound, [Zn3 (C40 H24 N8 )(C20 H8 N2 O4 )2 (DEF)2 ](DEF)3 (1; DEF=N,N-diethylformamide), has been synthesized by employing 5,10,15,20-tetrakis(4-pyridyl)porphyrin, 1,2-diamino-3,6-bis(4-carboxyphenyl)benzene, and Zn2+ salt at 100 °C under solvothermal conditions. The structure, as determined by single-crystal XRD studies, is three-dimensional with threefold interpenetration. The usefulness of free -NH2 groups in the ligand was exploited for anchoring silver nanoparticles through a simple solution-based route. The silver-loaded sample, Ag@1, was characterized by powder XRD, energy-dispersive X-ray spectroscopy, high-resolution TEM, SEM, X-ray photoelectron spectroscopy, and inductively coupled plasma MS analysis, which clearly indicated that silver nanoparticles with a size of 3.83 nm were uniformly distributed within the metal-organic framework (MOF). The Ag@1 sample was evaluated for possible catalytic activity for the carboxylation of a terminal alkyne by employing CO2 under atmospheric pressure; this gave excellent results. The Ag@1 catalyst was found to be robust, active, and recyclable. The present studies suggest that porphyrin MOFs not only exhibit interesting structures, but also show good heterogeneous catalytic activity towards the fixation of CO2 .