34 research outputs found
DALTON Spectral, magnetic and electrochemical properties of metal oxa-and oxathia-porphyrins ā
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 ā ā 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reports 2 exist on the synthesis of oxaporphyrins and mixed oxathiaporphyrins in which one or more pyrrole rings have been replaced by furan rings and/or thiophene rings.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- ā Non-SI units employed: G = 10 ĻŖ4 T, Āµ B ā 9.27 Ć 10 ĻŖ24 J T ĻŖ1 . 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 Īµ 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 UVĆ¢ā¬āvis 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.Ć
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
coreāaniline-based benzoxazines (IBPA-Bz) and imidazole coreāDMAPA-based
benzoxazines (IBPD-Bz), possess better glass temperatures (<i>T</i><sub>g</sub>) 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><sub>p</sub>) 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 (4,4ā²-diaminodiphenylsulfone-
and 4,4ā²-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><sub>p</sub> was reduced
without significant variation in the thermal behavior, i.e., a reduction
of more than 35 Ā°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 NāDoped Graphene Wrapped CoMn<sub>2</sub>O<sub>4</sub> 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 gā1 (1059 F cmā3) at
0.5 A gā1 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 kgā1 at 123 and
7407 W kgā1, 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 NāDoped Graphene Wrapped CoMn<sub>2</sub>O<sub>4</sub> 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 gā1 (1059 F cmā3) at
0.5 A gā1 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 kgā1 at 123 and
7407 W kgā1, 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