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1.
Zootaxa ; 5087(2): 357-371, 2022 Jan 06.
Article in English | MEDLINE | ID: mdl-35390913

ABSTRACT

Corallana mishrai sp. nov. collected from dead mangrove roots at Kodiyaghat, South Andaman, Andaman Islands, India is described and illustrated in detail. Corallana mishrai sp. nov. the first definitive record of the genus from India, is characterized by: frontal lamina with short straight (or very weakly convex) lateral margins and the anterior margin forming a strong acute median point; pleotelson length 0.76 greatest width, posterior margin with 5 robust setae; uropodal exopod 7 times longer than greatest width, extending beyond endopod by one fourth of its length; endopod lateral margin slightly convex with 4 RS and PMS, apex forms a slightly obtuse angle with long simple setae, mesial margin weakly convex with 2 RS and PMS; mandible bidentate; transverse row of 6 tubercles present on pereonite 1 and pleonites 2, 3 and 4 lacking lateral tubercles. The status of the genus and its species are reviewed, and two species are transferred to new combinations: Argathona kulai (Bruce, 1982) comb. nov. and Tachaea bidentata (Jones et al. 1983) comb. nov.


Subject(s)
Coleoptera , Isopoda , Animals , Indian Ocean , Islands
2.
Plant Cell Rep ; 40(4): 621-635, 2021 Apr.
Article in English | MEDLINE | ID: mdl-33449143

ABSTRACT

KEY MESSAGE: A deletion created by CRISPR/Cas9 system in the 5' UTR of the carotenoid isomerase gene in tomato leads to downregulation of the gene resulting in the low conversion of prolycopene to lycopene. CRISPR/Cas9 based genome editing is an effective and useful tool adopted from the bacterial immune response system for altering specific, pre-determined DNA sequences in eukaryotes. Such targeted changes are finding wide application in human health as well as in precision breeding of crop plants for improved traits. Mutations in the coding and regulatory regions can have varying impacts on the function of the gene. In the current study, we demonstrate this on tomato carotenoid isomerase, a key gene in the carotenoid biosynthesis pathway. Mutations were generated in the 5' UTR and exon 1 of the carotenoid isomerase gene using CRISPR/Cas9 expression via Agrobacterium-mediated transformation of tomato variety Periyakulam 1 (PKM1). Molecular and biochemical studies demonstrate that CRISPR-mediated point mutations in the exon sequence lead to complete knockout of protein function whereas deletion in 5' UTR region lowers the expression of the gene leading to changes in plant phenotype.


Subject(s)
5' Untranslated Regions , Plant Proteins/genetics , Solanum lycopersicum/genetics , cis-trans-Isomerases/genetics , Agrobacterium/genetics , Carotenoids/metabolism , Chlorophyll/genetics , Chlorophyll/metabolism , Gene Editing/methods , Gene Expression Regulation, Plant , Lycopene/metabolism , Solanum lycopersicum/physiology , Mutation , Plant Leaves/genetics , Plant Leaves/metabolism , Plant Proteins/metabolism , Plants, Genetically Modified , cis-trans-Isomerases/metabolism
3.
Zootaxa ; 4860(4): zootaxa.4860.4.4, 2020 Oct 14.
Article in English | MEDLINE | ID: mdl-33055880

ABSTRACT

Aphantolana wandoor sp. nov. is described from intertidal algae in South Andaman, Andaman Islands. Aphantolana wandoor sp. nov. is characterized by the uropodal exopod posterolateral margin with a slight concavity, mesial margin evenly convex with 2 robust setae, pleotelson posterolateral lateral margin concave, weakly sinuate.


Subject(s)
Isopoda , Animals , Indian Ocean , Islands
4.
Int J Biol Macromol ; 93(Pt A): 731-745, 2016 Dec.
Article in English | MEDLINE | ID: mdl-27601132

ABSTRACT

In this study, 27 strains of Lactic acid bacteria (LAB) were isolated and identified from different milk sources. All the isolates were biochemically characterized and screened for their ability to produce exopolysaccharides (EPS), among which two isolates namely Lactobacillus plantarum NTMI05 (197mg/L) and Lactobacillus plantarum NTMI20 (187mg/L) showed higher EPS production. Both the isolates were molecular characterized and tested for their probiotic properties. The chemical composition of EPS from L. plantarum NTMI05 and NTMI20 revealed the presence of 95.45% and 92.35% carbohydrates, 14±0.1and 11±0.15mg/L lactic acid, 10.5±0.2 and 9±0.1mg/mL of reducing sugar, respectively. HPLC analysis showed galactose at the retention time of 2.29.The maximum EPS yield was optimized for the media components like glucose (20g/L), yeast extract (25g/L) and ammonium sulphate (2g/L) using Central Composite Design and Response Surface Methodology (RSM). Under optimum conditions the predicted maximum EPS production was 0.891g/L, 0.797g/L, while the actual experimental value was 0.956g/L and 0.827g/L for L. plantarum NTMI05 and NTMI20, respectively. The antioxidant capacity was also evaluated by DPPH and reducing power assay proving the potentiality of these organisms in food and dairy industries.


Subject(s)
Antioxidants/chemistry , Lactobacillus plantarum , Polysaccharides, Bacterial , Probiotics/chemistry , Lactobacillus plantarum/chemistry , Lactobacillus plantarum/metabolism , Polysaccharides, Bacterial/biosynthesis , Polysaccharides, Bacterial/chemistry
6.
Colloids Surf B Biointerfaces ; 106: 1-10, 2013 Jun 01.
Article in English | MEDLINE | ID: mdl-23434685

ABSTRACT

In the wake of adoption of the resolution by the International Maritime Organization to control biofouling on vessels, which is recognized as a major vector for transfer of invasive species, this study attempts to create a baseline data on major hard-shelled biofouling organisms in the harbour waters. This study was primarily focused towards understanding the biofouling and corrosion pattern on various metals and their performance under immersed condition in a marine environment, at 0.3 and 3.0m depths. Furthermore, the study attempts to understand the surface dependent characteristics of barnacle base plate and its adhesion strength. Barnacle, mussels and oysters were the major fouling organisms accounting for 72.33% of the variation. Stainless steel and Titanium panels showed the highest average biofouling load of 176.36 and 168.35 g/300 cm(2), respectively. The variance in biofouling between metals and depths was highly significant at p<0.001 and p<0.01, respectively. Morphology of barnacle base plate interfacial surface varied between metals. Barnacles with 8-9 mm base diameter showed the maximum adhesion strength in shear of 6.86±0.95 kPa.


Subject(s)
Biofouling , Marine Biology , Thoracica/physiology , Animals , Bacteria/isolation & purification , Biofilms , Colony Count, Microbial
7.
Colloids Surf B Biointerfaces ; 91: 205-11, 2012 Mar 01.
Article in English | MEDLINE | ID: mdl-22143025

ABSTRACT

Biofouling on six different (silicone rubber, polydimethylsiloxane, polypropylene, high density polyethylene, polyvinylchloride, and polycarbonate) substrata with varying surface energy (18-40 mN/m) and surface roughness (R(a) 45-175 µm) was studied in the Eastern coastal waters of India over a short period of time (3 days). The results showed that the substrata surface energy (SE) followed by the surface roughness (R(a)) had profound effect on attachment of fouling organisms. After one day of immersion, viable count of bacteria in the biofilm was positively correlated with surface energy (r=0.69, p<0.05) and not with surface roughness (r=-0.02) of the substratum. Whereas, Pseudomonas count was inversely correlated with surface energy (r=-0.66, p<0.05) and surface roughness (r=-0.52, p<0.05). The attachment of macrofouler and the surface characteristics were also well correlated with SE 0.48 and with roughness 0.62, p<0.05. A positive correlation was observed amongst the various biofouling constituents such as bacteria, ATP, carbohydrates and organic matter on almost all the substrata. However after the first day, the surface characteristics of the substratum became less important and the conditioning film that was formed on the substrata appeared to directly influence further fouling on the surfaces, as evidenced by poor correlation between surface energy and macrofouler attachment (r=-0.11). The observation of high numbers of Hydroides elegans on PVC could be solely due to the influence of surface roughness (r=0.62). Though there is no marked difference in the 'primary film', and the composition of the biofilm, the amount of attached macrofouler is minimal on silicone rubber and polydimethylsiloxane on subsequent days of immersion, which reveals the foul release quality of these substrata probably due to their flexible nature.


Subject(s)
Polymers/chemistry , Seawater , Biomass , Colony Count, Microbial , India , Pseudomonas/growth & development , Surface Properties
8.
Environ Monit Assess ; 176(1-4): 239-50, 2011 May.
Article in English | MEDLINE | ID: mdl-20717718

ABSTRACT

The study addresses the distribution and diversity of mesozooplankton near the active volcano-Barren Island (Andaman Sea) in the context of persistent volcanic signature and warm air pool existing for the last few months. Sampling was done from the stations along the west and east side of the volcano up to a depth of 1,000 m during the inter monsoon (April) of 2006. Existence of feeble warm air pool was noticed around the Island (Atm. Temp. 29°C). Sea surface temperature recorded as 29.9°C on the west and 29.6°C on the east side stations. High mesozooplankton biomass was observed in the study area than the earlier reports. High density and biomass observed in the surface layer decreased significantly to the deeper depths. Lack of correlation was observed between mesozooplankton biomass and density with chl. a. Twenty-three mesozooplankton taxa were observed with copepoda as the dominant taxa followed by chaetognatha. The relative abundance of chaetognatha considerably affected the copepod population density in the surface layer. A noticeable feature was the presence of cumaceans, a hyperbenthic fauna in the surface, mixed layer and thermocline layer on the western side station where the volcano discharges in to the sea. The dominant order of copepoda, the calanoida was represented by 52 species belonging to 17 families. The order poecilostomatoida also had a significant contribution. Copepods exhibited a clear difference in their distribution pattern in different depth layers. The families Calanidae and Pontellidae showed a clear dominance in the surface whereas small-sized copepods belonging to the families Clausocalanidae and Paracalanidae were observed as the predominant community in the mixed layer and thermocline layer depth. Families Metridinidae, Augaptilidae and Aetideidae were observed as dominant in deeper layers.


Subject(s)
Geography , Volcanic Eruptions , Zooplankton/isolation & purification , Animals , Oceans and Seas , Zooplankton/classification
9.
Colloids Surf B Biointerfaces ; 74(1): 75-83, 2009 Nov 01.
Article in English | MEDLINE | ID: mdl-19647419

ABSTRACT

Titania, niobia and silica coatings, derived from their respective nanoparticle dispersions or sols and fabricated on soda lime glass substrates were subjected to field testing in marine environment for antimacrofouling applications for marine optical instruments. Settlement and enumeration of macrofouling organisms like barnacles, hydroides and oysters on these nanoparticle-based metal oxide coatings subjected to different heat treatments up to 400 degrees C were periodically monitored for a period of 15 days. The differences observed in the antifouling behaviour between the coated and uncoated substrates are discussed based on the solar ultraviolet light induced photocatalytic activities as well as hydrophilicities of the coatings in case of titania and niobia coatings and the inherent hydrophilicity in the case of silica coating. The effect of heat treatment on the photocatalytic activity of the coatings is also discussed.


Subject(s)
Biofouling , Coated Materials, Biocompatible/chemistry , Glass/chemistry , Metals/chemistry , Nanoparticles/chemistry , Oxides/chemistry , Seawater/chemistry , Adhesiveness/radiation effects , Animals , Biofilms/growth & development , Biofilms/radiation effects , Calcium Compounds/chemistry , Catalysis/radiation effects , Colony Count, Microbial , Hot Temperature , Marine Biology , Nanoparticles/ultrastructure , Ostreidae/physiology , Powders , Sodium Hydroxide/chemistry , Spectrum Analysis , Thoracica/physiology , Titanium/chemistry , Ultraviolet Rays , Water/chemistry , X-Ray Diffraction
10.
J Am Chem Soc ; 131(17): 6114-23, 2009 May 06.
Article in English | MEDLINE | ID: mdl-19354244

ABSTRACT

The oxidation of guanine to 5-carboxamido-5-formamido-2-iminohydantoin (2-Ih) is shown to be a major transformation in the oxidation of the single-stranded DNA 5-mer d(TTGTT) by m-chloroperbenzoic acid (m-CPBA) and dimethyldioxirane (DMDO) as a model for peracid oxidants and in the oxidation of the 5-base pair duplex d[(TTGTT).(AACAA)] with DMDO. 2-Ih has not been reported as an oxidative lesion at the level of single/double-stranded DNA or at the nucleoside/nucleotide level. The lesion is stable to DNA digestion and chromatographic purification, suggesting that 2-Ih may be a stable biomarker in vivo. The oxidation products have been structurally characterized and the reaction mechanism has been probed by oxidation of the monomeric species dGuo, dGMP, and dGTP. DMDO selectively oxidizes the guanine moiety of dGuo, dGMP, and dGTP to 2-Ih, and both peracetic and m-chloroperbenzoic acids exhibit the same selectivity. The presence of the glycosidic bond results in the stereoselective induction of an asymmetric center at the spiro carbon to give a mixture of diastereomers, with each diastereomer in equilibrium with a minor conformer through rotation about the formamido C-N bond. Labeling studies with [(18)O(2)]-m-CPBA and H(2)(18)O to determine the source of the added oxygen atoms have established initial epoxidation of the guanine 4-5 bond with pyrimidine ring contraction by an acyl 1,2-migration of guanine carbonyl C6 to form a transient dehydrodeoxyspiroiminodihydantoin followed by hydrolytic ring-opening of the imidazolone ring. Consistent with the proposed mechanism, no 8-oxoguanine was detected as a product of the oxidations of the oligonucleotides or monomeric species mediated by DMDO or the peracids. The 2-Ih base thus appears to be a pathway-specific lesion generated by peracids and possibly other epoxidizing agents and holds promise as a potential biomarker.


Subject(s)
Chlorobenzoates/chemistry , DNA/chemistry , Epoxy Compounds/chemistry , Hydantoins/chemistry , Oxidants/chemistry , Guanine/chemistry , Magnetic Resonance Spectroscopy , Oxidation-Reduction , Time Factors
11.
Environ Monit Assess ; 127(1-3): 459-75, 2007 Apr.
Article in English | MEDLINE | ID: mdl-16897497

ABSTRACT

The paper deals with the standing stock of macrobenthic infauna and associated environmental factors influencing the benthic community in the shelf region of the northwest Indian coast. The data were collected onboard FORV Sagar Sampada during the winter monsoon (January-February, 2003) to understand the community structure and the factors influencing the benthic distribution. The environmental parameters, sediment characteristics and macrobenthic infauna were collected at 26 stations distributed in the depths between 30 and 200 m extending from Mormugao to Porbander. Total benthic abundance was high in lower depths (50-75 m), and low values noticed at 30 m depth contour was peculiar. Polychaetes were the dominant group and were more abundant in shallow and middle depths with moderate organic matter, clay and relatively high dissolved oxygen. On the other hand crustaceans and molluscs were more abundant in deeper areas having sandy sediment and low temperature. High richness and diversity of whole benthic groups observed in deeper depths counter balanced the opposite trend shown by polychaete species. Generally benthos preferred medium grain sized texture with low organic matter and high organic matter had an adverse effect especially on filter feeders. Deposit feeding polychaetes dominated in shallow depths while carnivore species in the middle depths. Ecologically, benthos were controlled by a combination of factors such as temperature, salinity, dissolved oxygen, sand and organic matter and no single factor could be considered as an ecological master factor.


Subject(s)
Biodiversity , Environmental Health , Environmental Monitoring , Geography , India , Seawater
12.
Chem Res Toxicol ; 19(4): 506-10, 2006 Apr.
Article in English | MEDLINE | ID: mdl-16608161

ABSTRACT

The nucleobase guanine was oxidized with dimethyldioxirane (DMDO) to explore the role of epoxidizing agents in oxidative DNA damage. Treatment of guanine with 10% molar excess DMDO in aqueous solution at 0 degrees C and pH 7.5 followed by workup under mild conditions gave 5-carboxamido-5-formamido-2-iminohydantoin (1) as the sole isolable product in 71% yield. The structure of 1 was established on the basis of mass spectrometry and NMR studies on 1 and its isotopomers generated by the oxidation of [4-(13)C] and [7-(15)N]guanine, which yield [5-(13)C]1 and [7-(15)N]1. The distribution of 13C and 15N labels in the isotopomeric products supports initial epoxidation of the C4-C5 bond of guanine followed by a 1,2-acyl migration of guanine C6. Compound 1 is suggested as a possible primary DNA lesion from putative epoxidizing agents, including hydroperoxides present during biological processes such as lipid peroxidation.


Subject(s)
Guanine/chemistry , Imines/chemistry , Spiro Compounds/chemistry , Magnetic Resonance Spectroscopy , Oxidation-Reduction , Spectrometry, Mass, Electrospray Ionization
13.
Photochem Photobiol ; 80(2): 294-300, 2004.
Article in English | MEDLINE | ID: mdl-15362943

ABSTRACT

Porphyrins are photosensitizers and may be applicable in situations where viral inactivation is required, as for in vitro inactivation of nonenveloped viruses in blood components or in other aqueous media. No study has examined the efficacy of porphyrin inactivation on human pathogens such as hepatitis A virus (HAV) in plasma or other liquids. Experiments were conducted to evaluate the effect of synthetic porphyrins on HAV in porphyrin-containing human plasma and phosphate-buffered saline exposed to long-wavelength (365 nm) UV light. Inactivation of bacteriophage MS2 (MS2) also was determined in some trials. Solutions containing cationic, anionic or amphiphilic porphyrins irradiated with an average light dose of 4.3 J/cm(2) for 90 min resulted in >3 log(10) (>99.9%) to >4 log(10) (>99.99%) inactivation of both HAV and MS2. Viral inactivation may have been greater than observed because the limits of detection of the assay had been reached. Under ambient lighting conditions, none of the porphyrins was mutagenic in the Ames assay and only the congener with the longest chain-length, tetrakis (N-[n-hexadecyl]-4-pyridiniumyl) porphyrin, was appreciably toxic to mammalian cells. Disinfection by photoactivated synthetic porphyrins therefore can offer an effective and relatively safe approach to removal of nonenveloped viruses from aqueous media.


Subject(s)
Hepatitis A virus/drug effects , Hepatitis A virus/radiation effects , Photosensitizing Agents/pharmacology , Porphyrins/chemical synthesis , Porphyrins/pharmacology , Virus Inactivation/drug effects , Virus Inactivation/radiation effects , Hepatitis A virus/physiology , Humans , Ions/chemistry , Molecular Structure , Photosensitizing Agents/chemical synthesis , Photosensitizing Agents/chemistry , Photosensitizing Agents/toxicity , Plasma/drug effects , Plasma/radiation effects , Plasma/virology , Porphyrins/chemistry , Porphyrins/toxicity , Salmonella/drug effects
14.
Chem Res Toxicol ; 16(5): 637-43, 2003 May.
Article in English | MEDLINE | ID: mdl-12755593

ABSTRACT

1,3-Butadiene, a potential human carcinogen widely used in industry, is oxidized by cytochrome P450 to diepoxybutane (DEB), which is the most mutagenic of the known butadiene metabolites. Assessment of the toxicological significance of DEB formation in humans and animals requires identification of a biomarker uniquely associated with DEB for use in molecular dosimetry studies. We wished to develop a specific and sensitive assay for one such suitable marker, the cyclic adduct 2-(3,4-dihydroxypyrrolidin-1-yl)-3-methylbutyramide (pyr-V), which is formed from addition of DEB to the terminal Val of the alpha- and beta-chains of hemoglobin. We needed to prepare a pure, rigorously characterized DEB-modified N-terminal oligopeptide for raising antibodies both to use in an immunoaffinity purification step and to standardize the assay. In addition, we needed a pure isotopomer to serve as an internal standard for quantitation by LC-MS. Direct modification of the globin sequences by reaction with DEB in vitro proved to be unproductive. We therefore opted to synthesize the cyclic Val adduct and incorporate it by FMOC chemistry into the appropriate oligopeptide sequences. In vitro and in vivo, butadiene is oxidized to enantiomeric and meso forms of DEB. A priori, all three DEB isomers are expected to form pyr-V adducts, resulting in three diastereomeric N-terminal peptides. We therefore synthesized a mixture of the cyclic Val diastereomers as their methyl esters by reaction of DEB with l-Val methyl ester hydrochloride. After protection as the di-O-tert-butyl derivatives, the mixture of 2-(3,4-di-t-butoxypyrrolidin-1-yl)-3-methylbutyric acid diastereomers was incorporated as the N-terminal residue into the 1-11 human globin alpha-chain sequence VLSPADKTNVK. The presence of the three diastereomers was confirmed by two-dimensional correlation NMR spectroscopy and temperature-dependent (1)H NMR. This strategy enabled us to obtain pure, rigorously characterized haptens in quantity for the preparation of polyclonal antibodies. Use of FMOC-protected (2)H(3)-Leu in the automated oligopeptide synthesis provided the required isotopomers for use as internal standard.


Subject(s)
Amides/chemistry , Epoxy Compounds/chemistry , Oligopeptides/chemistry , Pyrrolidines/chemistry , Valine/chemistry , Amides/chemical synthesis , Biomarkers/chemistry , Butadienes/toxicity , Carcinogens/toxicity , Environmental Pollutants/toxicity , Globins/chemistry , Humans , Magnetic Resonance Spectroscopy , Oligopeptides/chemical synthesis , Pyrrolidines/chemical synthesis , Stereoisomerism
16.
N C Med J ; 61(4): 209-14, 2000.
Article in English | MEDLINE | ID: mdl-10917038

ABSTRACT

Our aging population is growing. As a result, dementia is becoming an ever more prevalent problem--with devastating consequences to the affected persons and their families. In the evaluation of the demented patient, it is crucial to look for and exclude conditions such as depression and other reversible causes of cognitive impairment before branding the patient with a diagnosis of dementia. Drug treatment of AD is not highly successful, although the Food and Drug Administration has approved acetylcholinesterase inhibitors for the treatment of mild to moderate AD. Present-day treatment for dementia focuses mainly on improving or preserving the quality of life of patients and their families, and on treating concomitant psychosocial, behavioral, and medical issues. We are optimistic that new, innovative medications may in the future allow us to treat or even cure Alzheimer's disease and other progressive dementing disorders.


Subject(s)
Alzheimer Disease/diagnosis , Dementia/diagnosis , Alzheimer Disease/therapy , Dementia/therapy , Humans
17.
Inorg Chem ; 39(16): 3652-64, 2000.
Article in English | MEDLINE | ID: mdl-11196829

ABSTRACT

This report describes the synthesis and characterization of a series of octaethylporphyrin derivatives in which the porphyrin pi-network is connected to phenyl, 3-fluoranthenyl, or 1-pyrenyl aromatic systems through a meso amino or amido nitrogen. Metal-free bases and zinc(II) and iron(III) complexes have been obtained. These compounds represent the first examples of linkages between porphyrins and extended pi-networks through a nitrogen atom directly attached to a porphyrin meso position. 1H NMR studies of the metal-free bases and zinc complexes showed that in the amido-linked adducts, the plane containing the aryl substituent was oriented perpendicular to the plane of the porphyrin. Linkage through the secondary amino nitrogen, however, allowed the aryl plane to rotate toward coplanarity with the porphyrin plane, resulting in conjugation of the highest occupied aryl and porphyrin molecular orbitals through the nitrogen lone pair. In developing routes to the amino-linked compounds, the facile formation of fused azaaryl chlorins via an oxidative intramolecular cycloaddition was observed. An aryl carbon ortho to the meso linkage attacked the beta-carbon of an adjacent pyrrole ring, accompanied by 1,2-migration of a pyrrole beta-ethyl substituent and a two-electron oxidation of the initially formed macrocycle. The resulting structures are analogous to benzochlorins. The electronic spectra of the metal-free bases are characterized by intense, long-wavelength bands in the visible region. Molecular structures of the chloroferric complexes of the azabenzofluorantheno- and azabenzpyrenoporphyrin macrocycles (derived from fusion of the fluoranthenyl and pyrenyl substituents, respectively) were obtained by X-ray diffraction. The porphyrin moiety in the azabenzofluoranthenoporphyrin adopted a gable structure, with a 22 degrees fold along a diagonal including the pyrrole-ring C4 and C16 alpha-carbons. By contrast, the azabenzpyrenoporphyrin was virtually planar.


Subject(s)
Nitrogen/chemistry , Porphyrins/chemistry , Hemoglobins/chemistry , Magnetic Resonance Spectroscopy , Molecular Conformation , Myoglobin/chemistry , Photosynthesis
18.
Inorg Chem ; 39(3): 532-40, 2000 Feb 07.
Article in English | MEDLINE | ID: mdl-11229573

ABSTRACT

The perchloratoiron(III) complexes of a series of 2,6-disubstituted tetraphenylporphyrin ligands, where the 2,6-phenyl substituents were -H, -F, -Cl, -Br, or -OMe, as well as two 2,4,6-phenyl-substituted complexes, where the substituents were -Me and -OMe, have been investigated as a function of temperature by 1H NMR spectroscopy. Curvature in the 1/T dependence was evident in most cases. Forced linear extrapolation of the temperature dependence observed over the range of the study yielded Curie plots that include negative slopes with very large positive 1/T intercepts (Cl approximately Br > Me > H) to negative slope with near zero intercept (tri-OMe) to positive slope with very large negative intercept (F, di-OMe). The NMR results were combined with EPR spectroscopic data and curve-fitting procedures based on an expanded Curie law to arrive at a consistent overview of the variety of temperature-dependence behaviors observed. This overview relies upon the premise that, in addition to the ground state observed by EPR spectroscopy, one (or more) thermally accessible excited state(s) are populated to varying degrees over the temperature range of the NMR measurements. If only one excited state is considered, the analysis is consistent with the ground state being a largely intermediate-spin state (S = 3/2) for the majority of the complexes but a largely high-spin state (S = 5/2) for ((2,6-F2)4TPP)FeOClO3 and ((2,6-(OMe)2)4TPP)FeOClO3.


Subject(s)
Metalloporphyrins/chemistry , Electron Spin Resonance Spectroscopy , Electrons , Nuclear Magnetic Resonance, Biomolecular , Temperature
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