DALTON Spectral, magnetic and electrochemical properties of metal oxa-and oxathia-porphyrins †

Metal derivatives (Cu II , Ni II ) of monooxa-, dioxa-and oxathia-tetraphenylporphyrins and their one-electron oxidised and reduced species have been studied. Electronic spectra of the monooxa and oxathia derivatives exhibit split Soret bands and a complicated pattern of Q-bands revealing their lower symmetry. The spectra of one-electron reduced species show only marginal shifts while the one-electron oxidised product of copper monooxaporphyrins show broad, red-shifted bands. Cyclic voltammetric studies indicated one-electron metalcentered reduction at fairly low potentials forming copper() and nickel() porphyrins. The ring-oxidised product exhibits weak antiferromagnetic interaction between the unpaired electrons of copper and the porphyrin ring. The ESR spectra of the copper dioxa-and oxathia-porphyrins exhibit rhombic symmetry with unusually small metal hyperfine couplings. A comparison of A Cu values and the E ₂ ₁ values for metal reduction suggests that distortion towards tetrahedral symmetry and the presence of a soft donor atom like sulfur in porphyrins are required to generate spectral and electrochemical properties like those observed for the type I copper center in proteins. Replacement of pyrrole N atoms in the porphyrin core by other heteroatoms such as S, Se, Te and O alters the core sizes and electronic structure. The crystal structure of nickel() thiaporphyrin revealed a distorted square pyramid around the metal with an axial chloride ligand, leading to five-co-ordination. 7, 11 However, relatively few reports 2 exist on the synthesis of oxaporphyrins and mixed oxathiaporphyrins in which one or more pyrrole rings have been replaced by furan rings and/or thiophene rings. To the best of our knowledge there are only two recent reports on the metal (Ni II ) binding properties of oxaporphyrins by Latos-Grazynski and co-workers 12 and Gross et al. 14 Further, our recent study 15 on free base oxa- † Non-SI units employed: G = 10 Ϫ4 T, µ B ≈ 9.27 × 10 Ϫ24 J T Ϫ1 . and oxathia-porphyrins revealed that the oxaporphyrins behave more like the parent tetraphenylporphyrin in their spectroscopic properties while their electrochemical properties resemble those of thiaporphyrins. In this paper we report the metal binding (Cu II and Ni II ) properties of monooxa-, dioxa-and oxathia-porphyrins and their one-electron reduced and oxidised species. Specifically, electronic absorption spectra have been used to study groundstate properties while the redox chemistry has been monitored by cyclic voltammetry. The changes occurring in the electron delocalisation pathway and the metal-ligand bond strength upon binding of Cu II have been studied by ESR spectroscopy. It has been shown that the first reduction is metal centered, corresponding to the formation of complexes of Cu I and Ni I , while the first oxidation of copper monoxaporphyrins is ring based with a weak antiferromagnetic coupling between the metal and the ring unpaired electrons. Results The metallation of oxaporphyrins can readily be done using literature methods. 12 The copper() and nickel() derivatives of monooxa and monothia derivatives are stable both in the solid and solution states, the dioxa derivative on a chromatographic column undergoing gradual demetallation while the oxathia derivative on standing for few hours in the solid decomposes to give the corresponding free base porphyrin. The electronic absorption spectra of various neutral, one-electron-reduced and -oxidised copper oxaporphyrins are shown in 14 The ε values are significantly reduced for the core-modified porphyrins relative to the parent [M(tpp)]. 16 The EPR spectra of the copper porphyrins described here were recorded in toluene-CH 2 Cl 2 (1 : 1) at room and liquid nitrogen temperature

GREEN SYNTHESIS, CHARACTERIZATION, ANTIMICROBIAL AND CYTOTOXIC EFFECTS OF SILVER NANOPARTICLES USING ORIGANUM HERACLEOTICUM L. LEAF EXTRACT

Objectives: Silver nanoparticles (AgNPs) possess unique features among noble metal nanoparticles due to their wide range of applications in various field including medicine, environmental safety, etc. The present study relies on eco-friendly, cost effective method for the synthesis of AgNPs.Methods: AgNPs were rapidly synthesized from AgNO3 using aqueous leaf extract of O. heracleoticum L. as reducing as well as capping agent. Synthesized AgNPs were characterized with the help of FE-SEM, XRD, EDS and UV–vis absorption spectroscopy. FE-SEM showed the spherical nature of nanoparticles with the size ranging from 30-40 nm. In addition, their antibacterial activities against standard bacterial pathogens were evaluated as per the standard disk diffusion method. Further, cytotoxicity potential of AgNPs were also determined using the MTT assay.Results: X-ray diffraction analysis showed that the nanoparticles formed in the present synthesis were crystalline in nature. FT-IR analysis showed the presence of possible biomolecules needed for reducing silver ions. Further, antibacterial activity of synthesized AgNPs showed effective inhibition against pathogenic microbes. In addition, these green synthesized nanoparticles were shown to exhibit potential cytotoxic effect on MCF-7 cell line in dose dependent manner.Conclusion: It has been demonstrated that O. heracleoticum L. plant extract could be used as a proficient green reducing agent for the synthesis of AgNPs. Further, these synthesized AgNPs were shown to exhibit effective antibacterial effect against pathogens and potential cytotoxic effect on MCF-7 cells.Â

Novel heteroatom containing rubyrins

Synthesis of rubyrins containing two or three heteroatoms (O, S, Se) in the core is accomplished using modified diols and tetrapyrromethanes. Substitution of heteroatoms leads to significant reductions in HOMO-LUMO gap and easier oxidations and reductions reflecting the changes in electronic structure of the rubyrin skeleton

One step synthesis of sapphyrin and N-confused porphyrin using dipyrromethane

Reaction of dipyrromethane in trifluoroacetic acid produces sapphyrin while the same reaction in toluene p-sulfonic acid gave N-confused porphyrin

A Novel Imidazole-Core-Based Benzoxazine and Its Blends for High-Performance Applications

In the present work, a novel imidazole-core-based bisphenol (IBP) was synthesized and characterized. The IBP and formaldehyde were reacted separately with aniline and <i>N</i>,<i>N</i>-dimethylaminopropylamine (DMAPA) under appropriate conditions to obtain benzoxazines, which were characterized for their molecular structure and thermal behavior using different analytical methods. Both types of benzoxazines, imidazole core–aniline-based benzoxazines (IBPA-Bz) and imidazole core–DMAPA-based benzoxazines (IBPD-Bz), possess better glass temperatures (<i>T</i>_g) and higher char yields than conventional benzoxazines (bisphenol-F-based benzoxazine (BPFb) and bisphenol-A-based benzoxazine (BPAb)). However, the curing temperature (<i>T</i>_p) of IBPD-Bz is lower than that of IBPA-Bz. The blending of IBPA-Bz with conventional benzoxazines (BPAb and BPFb) improved their thermal stability to an appreciable extent. Furthermore, the addition of bismaleimide cross-linkers (4,4′-diaminodiphenylsulfone- and 4,4′-diaminodiphenylmethane-based bismaleimides) to the blends of IBPA-Bz and conventional benzoxazines improved the thermal behavior according to their nature and concentration. Moreover, the selected blends of benzoxazines were incorporated with 10% loadings of catalysts (4-hydroxyphenylmaleimide, 4-aminophenol, and 4-hydroxyacetophenone), and it was observed that <i>T</i>_p was reduced without significant variation in the thermal behavior, i.e., a reduction of more than 35 °C was noticed for both conventional benzoxazines. On the basis of the data obtained from the different studies, it is concluded that the blends of IBPA-Bz and conventional benzoxazines can be used in the form of sealants, encapsulants, adhesives, and matrixes in the fields of microelectronic and automobile applications for better performance with enhanced longevity

High-Performance Mg-Ion Supercapacitor Designed with a N‑Doped Graphene Wrapped CoMn₂O₄ and Porous Carbon Spheres

Mg-ion supercapacitors (SCs) can be a potential candidate for advanced electrochemical energy storage devices because they are low-cost and safe and have long-term cycling stability. However, exhibiting high energy density while preserving high power density is still a challenge for Mg-ion supercapacitors, which limits their practical applications. Herein, we proposed cathode CoMn2O4 nanospheres embedded in N-doped graphene (CMO/G-N) and prepared via an improvised hydrothermal route. The material exhibited a capacitance of 691 F g–1 (1059 F cm–3) at 0.5 A g–1 in an aqueous Mg(ClO4)2 electrolyte. Additionally, as fabricated, the flexible Mg-ion asymmetric supercapacitor CMO/G-N//PCS (FMASC) exhibits energy and power densities of 61 and 34 W h kg–1 at 123 and 7407 W kg–1, respectively, with 87% retention of capacitance after 10,000 cycles. This study provides a neoteric perspective on building flexible energy storage devices using novel Mg-ion electrolytes

High-Performance Mg-Ion Supercapacitor Designed with a N‑Doped Graphene Wrapped CoMn₂O₄ and Porous Carbon Spheres

Mg-ion supercapacitors (SCs) can be a potential candidate for advanced electrochemical energy storage devices because they are low-cost and safe and have long-term cycling stability. However, exhibiting high energy density while preserving high power density is still a challenge for Mg-ion supercapacitors, which limits their practical applications. Herein, we proposed cathode CoMn2O4 nanospheres embedded in N-doped graphene (CMO/G-N) and prepared via an improvised hydrothermal route. The material exhibited a capacitance of 691 F g–1 (1059 F cm–3) at 0.5 A g–1 in an aqueous Mg(ClO4)2 electrolyte. Additionally, as fabricated, the flexible Mg-ion asymmetric supercapacitor CMO/G-N//PCS (FMASC) exhibits energy and power densities of 61 and 34 W h kg–1 at 123 and 7407 W kg–1, respectively, with 87% retention of capacitance after 10,000 cycles. This study provides a neoteric perspective on building flexible energy storage devices using novel Mg-ion electrolytes

Improved synthesis of meso substituted 21-oxa and 21-thia tetra phenyl porphyrins

An efficient method for the exclusive formation of 21-Oxa and 21-Thia tetra phenyl porphyrins in high yields by condensation of dipyrromethane and furan or thiophene diols is described