118 research outputs found
Cephalothoracoomphalopagus: A noninvasive study
No full textConjoined twins are rare variants of monozygotic twins, which result from an incomplete late division of the embryonic disc. Here, we report a rare case of conjoined twins of cephalothoracoomphalopagus variety where the line of fusion extended from the cranium up to the level of the umbilicus. The crown-rump length of each twin was 23 cm, which corresponded to the prenatal age of week 24 in a normal gravidity. The anatomical features of these conjoined twins were observed and external anomalies such as indefinite single nostril and male hypoplastic genitalia were described and documented. The old formalized specimen was studied to reveal anomalies by using current imaging techniques, thus keeping it intact for posterity. Computed tomography (CT) findings suggest cephalothoracopagus twinning, with the gestational age being 24 weeks (approximately). An attempt was made to correlate the findings on embryological basis
Magneto-structural studies of monohydroxo-ridged dicopper(II) complexes M[Cu<SUB>2</SUB>L<SUB>2</SUB>(OH)]·2H<SUB>2</SUB>O (M=Na<SUP>+</SUP> (1) and K<SUP>+</SUP> (2); H<SUB>2</SUB>L=2,6-bis[N-(phenyl)carbamoyl]pyridine). Effect of Cu---OH---Cu bridge angle on antiferromagnetic coupling
No full textUsing a tridentate bis-amide ligand 2,6-bis[N-(phenyl)carbamoyl]pyridine (H2L), in its deprotonated form, two new monohydroxo-bridged dicopper(II) complexes M[Cu2L2(OH)]·2H2O (M=Na+ (1) and K+ (2)) have been prepared and characterised by a number of methods, including X-ray crystallography. Each copper(II) ion is terminally coordinated by one pyridyl and two amide nitrogen donors. The two copper(II) centres are bridged by a hydroxo group, with each copper(II) centre assuming a distorted square planar geometry. The observation of short Cu---Npy and long Cu---Namide bonds is caused by the steric requirement of the ligand. Interestingly, each cation Na+/K+ is coordinated to four different [Cu2L2(OH)]- units through the amide O-donors, in an uncommon distorted tetrahedral coordination environment. Temperature-dependent magnetic susceptibility measurements revealed that the compounds have S=0 ground state with singlet-triplet energy separation, 2J=-334 and -296 cm-1 for 1 and 2, respectively. The larger Cu---OH---Cu bridge angle in 1 (131.1(6)°) causes better antiferromagnetic exchange coupling than that in 2 (125.7(6)°)
Synthesis and properties of a monomeric and a μ-oxo-bridged dimeric iron(III) complex with a tetradentate pyridine amide in-plane ligand. X-ray structure of [Fe(bpc)Cl(DMF)] [H2bpc=4,5-dichloro-1,2-bis(pyridine-2-carboxamido)benzene]
No full textThe controlled nucleophilic halide displacement reaction of
[NEt4][Fe(bpc)Cl2]
[H2bpc=4,5-dichloro-1,2-bis(pyridine-2-carboxamido) benzene] with AgClO4 in
MeCN afforded a crystalline iron(III) complex Fe(bpc)Cl·H2O 1. The mixed
chloro-dimethylformamide (DMF) axially ligated complex [Fe(bpc)Cl(DMF)] (obtained during
recrystallization of 1 from DMF; however, it loses DMF quite readily to revert back to 1) has been
structurally characterized. It belongs to only a handful of mononuclear high-spin iron(III) complexes
having deprotonated picolinamide ligand. The iron(III) centre is co-ordinated in the equatorial plane
by two pyridine nitrogens and two deprotonated amide nitrogens of the ligand, and two axial sites are
co-ordinated by a chloride ion and a DMF molecule. The metal atom has a distorted octahedral
geometry. Reaction of 1 with [nBu4N][OH] in MeOH afforded a μ-oxo-bridged
diiron(III) complex, [Fe(bpc)]2O·DMF·2H2O, 2. The spin state and the
co-ordination environment of the iron(III) centres in 1 and 2 have been determined by
temperature-dependent (25-300 K) magnetic susceptibility measurements in the solid state (Faraday
method) and Mossbauer spectral studies at 300 K. Complex 1 behaves as a perfect S=5/2 system, in the
solid-state as well as in DMF solution. The two iron(III) centres in 2 are antiferromagnetically
coupled (J=-117.8 cm-1) and the bridged dimeric structure is retained in DMF solution.
Bridge-cleavage reactions of 2 have been demonstrated by its ready reaction with mineral acids such
as HCl and MeCO2H to generate authentic S=5/2 complexes,
[Fe(bpc)Cl2]- and [Fe(bpc)(O2CMe)2]-,
respectively
Bivalent, Trivalent, and Tetravalent Nickel Complexes with a Common Tridentate Deprotonated Pyridine Bis-Amide Ligand. Molecular Structures of Nickel(II) and Nickel(IV) and Redox Activity
No full textUsing a tridentate bis-amide ligand 2,6-bis[N-(phenyl)carbamoyl]pyridine (H2L), in its deprotonated form, nickel
complexes in three consecutive oxidation states [Et4N]2[NiIIL2]·H2O (1), [Et4N][NiIIIL2]·H2O (2), and [NiIVL2]·0.75H2O (3) have been prepared, and 1 and 3 structurally characterized. These X-ray structures represent first
crystallographically characterized NiN6 coordination sphere, with a common pyridine bis-amide ligand. Complex
1 crystallizes in the orthorhombic space group Pccn, a = 10.175(2) Å, b = 20.834(3) Å, c = 23.765(4) Å, Z =
4, and 3 crystallizes in the monoclinic space group P21/a, a = 14.874(7) Å, b = 13.300(4) Å, c = 16.604(5) Å,
β = 99.678(3)°, Z = 4. Considerable distortion is observed with the average distances being Ni−Namide 2.131(8)
Å and Ni−Npy 1.994(7) Å for 1 and Ni−Namide 1.946(8) Å and Ni−Npy 1.846(8) Å for 3. The observation of
short axial M−Npy and long equatorial M−Namide bonds (tetragonally compressed octahedral geometry) is caused
by the steric requirement of the ligand. Magnetic susceptibility measurements (63−300 K) reveal that the spin
states of nickel centers in 1 and 2 are S = 1 and S = 1/2, respectively. Complex 3 is diamagnetic. In their absorption
spectra (MeCN), 1 exhibits a d−d transition at 854 nm; 2 and 3 display LMCT transitions at 449 nm with a
shoulder at 636 nm and at 480 nm with a shoulder at 730 nm, respectively. The nickel(III) complex 2 exhibits
a rhombic EPR signal (g values: 2.149, 2.115, and 2.034), showing that the metal center is the primary residence
site of the unpaired electron. Cyclic voltammetric measurements of 1 in MeCN solution at a glassy carbon electrode
exhibit two chemically reversible (ip,a/ip,c ≈ 1) and electrochemically quasireversible (ΔEp = 100 mV) oxidative
responses: a NiIII−NiII couple (E1/2 = 0.05 V vs SCE) and a NiIV−NiIII couple (E1/2 = 0.51 V vs SCE). A
one-electron chemical oxidation of yellowish brown 1 was achieved in a two-phase solvent mixture H2O−CH2Cl2 with [Fe(η5-C5H5)2][PF6], which led to the isolation of reddish brown 2. A two-electron chemical oxidation
of 1 was readily achieved in MeCN with ceric ammonium nitrate to afford dark violet crystals of 3. For 1 a linear
correlation between the NiIII−NiII reduction potentials and the reciprocal of solvent dielectric constants is obtained
Casteism in Practice: Some Personal Reflections
No full textIn this lecture, the author discussed caste on the basis of his personal, day-to-day experience. He also discusses the views of Gandhi, Ambedkar, and Tagore on caste
Ruthenium(II) Complexes of 4′‐(Aryl)‐2,2′:6′,2′′‐terpyridyl Ligands as Simple Catalysts for the Transfer Hydrogenation of Ketones
No full textCu(II) complexes with square pyramidal (N2S)CuCl2 chromophore: Jahn–Teller distortion and subsequent effect on spectral and structural properties
No full textBivalent, trivalent, and tetravalent nickel complexes with a common tridentate deprotonated pyridine bis-amide ligand. Molecular structures of nickel(II) and nickel(IV) and redox activity
No full textUsing a tridentate bis-amide ligand 2,6-bis[N-(phenyl)carbamoyl]pyridine (H2L), in its deprotonated form, nickel complexes in three consecutive oxidation states [Et4N]2[NiIIL2]·H2O (1), [Et4N][NiIIIL2]·H2O (2), and [NiIVL2]·0.75H2O (3) have been prepared, and 1 and 3 structurally characterized. These X-ray structures represent first crystallographically characterized NiN6 coordination sphere, with a common pyridine bis-amide ligand. Complex 1 crystallizes in the orthorhombic space group Pccn, α = 10.175(2) Å, b = 20.834(3) Å, c = 23.765(4) Å, Z = 4, and 3 crystallizes in the monoclinic space group P21/a, a = 14.874(7) Å, b = 13.300(4) Å, c = 16.604(5) Å, β = 99.678(3)°, Z = 4. Considerable distortion is observed with the average distances being Ni-Namide 2.131(8) Å and Ni-Npy 1.994(7) Å for 1 and Ni-Namide 1.946(8) Å and Ni-Npy 1.846(8) Å for 3. The observation of short axial M-Npy and long equatorial M-Namide bonds (tetragonally compressed octahedral geometry) is caused by the steric requirement of the ligand. Magnetic susceptibility measurements (63-300 K) reveal that the spin states of nickel centers in 1 and 2 are S = 1 and S =½, respectively. Complex 3 is diamagnetic. In their absorption spectra (MeCN), 1 exhibits a d-d transition at 854 nm; 2 and 3 display LMCT transitions at 449 nm with a shoulder at 636 nm and at 480 nm with a shoulder at 730 nm, respectively. The nickel(III) complex 2 exhibits a rhombic EPR signal (g values: 2.149, 2.115, and 2.034), showing that the metal center is the primary residence site of the unpaired electron. Cyclic voltammetric measurements of 1 in MeCN solution at a glassy carbon electrode exhibit two chemically reversible (ip,a/ip,c ≈ 1) and electrochemically quasireversible (ΔEp = 100 mV) oxidative responses: a NiIII-NiII couple (E½ = 0.05 V vs SCE) and a NiIV-NiIII couple (E½ = 0.51 V vs SCE). A one-electron chemical oxidation of yellowish brown 1 was achieved in a two-phase solvent mixture H2O-CH2Cl2 with [Fe(η5-C5H5)2][PF6], which led to the isolation of reddish brown 2. A two-electron chemical oxidation of 1 was readily achieved in MeCN with ceric ammonium nitrate to afford dark violet crystals of 3. For 1 a linear correlation between the NiIII-NiII reduction potentials and the reciprocal of solvent dielectric constants is obtained
Adverse Impact of Covid‐19 on Anatomical Sciences Teachers of India and Proposed Ways to Handle This Predicament
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