Shashi B. Kalia

Spectral and magnetic studies on normal cobalt(II) planar and cobalt(III) octahedral, spin-crossover cobalt(III) octahedral and planar-tetrahedral cobalt(II) carbodithioates

Abstract Five cobalt(II) complexes, a normal complex Co(4-PPipzcdt) 2 (4-PPipzcdt = 4-phenylpiperazine-1-carbodithioate), and four zwitterionic complexes, Co(4-PPipzcdtH) 2 X 2 and Co(4-MPipzcdtH) 2 X 2 (X = Cl, Br; 4-PPipzcdtH = 4-phenylpiperazine-1-carbodithioic acid, 4-MPipzcdtH = 4-methylpiperazine-1-carbodithioic acid), have been synthesized. Normal cobalt(III) complexes of the type Co(4-MPipzcdt) 3 and Co 2 {2-MPipz(cdt) 2 } 3 (2-MPipz(cdt) 2 = 2-methylpiperazine-1,4-dicarbodithioate) and two zwitterionic cobalt(III) complexes of the type Co(4-MPipzcdtH) 3 X 3 (X = Cl, Br) have also been obtained. In addition to the room temperature IR and electronic spectra and magnetic susceptibility studies, all the complexes, except the normal Co(4-MPipzcdt) 3 and Co(4-PPipzcdt) 2 and zwitterionic Co(4-MPipzcdtH) 3 Cl 3 , have been investigated by variable-temperature magnetic susceptibility measurements. The results of the variable-temperature magnetic susceptibility studies suggest that two cobalt(II) carbodithioates exhibit a square planar-tetrahedral equilibrium, while two cobalt(III) octahedral carbodithioates show a spin-crossover phenomenon.

Antimicrobial screening of some newly synthesised transition metal complexes of a dithiocarbazate derived from isoniazid

Some new metal (II) isonicotinoyldithiocarbazates of the general formula [M(IN-DtczH) 2 ]Cl 2 (M = Mn, Co, Ni, Zn; IN-DtczH = isonicotinoyldithiocarbazic acid) and Mn(IN-Dtcz) 2 , having sulphur-nitrogen linkage were synthesized. All the compounds were screened for their antimicrobial activity against the pathogenic bacteria Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Enterococcus sp . and the pathogenic fungus Candida albicans by agar dilution method. All the compounds showed good antimicrobial activity.

Substituent Effect on Carbodithioate Ligand Field Strength in Iron(III) Carbodithioates: Synthesis and Characterization

Abstract New iron(III) carbodithioate complexes of the general formulae Fe(Lcdt)3 [(where L is the anion of an heterocyclic amine and Lcdt are the following anions: 4-methylpiperazine-l-carbodithioate (4-MPipzcdt), 4-phenylpiperazine-l-carbodithioate (4-PPipzcdt), piperidinecarbodithioate (Pipdcdt), 2-methylpiperidine-carbodithioate (2-MPipdcdt), 4-methylpiperidine carbodithioate (4-MPipdcdt), morpholinecarbodithioate (Morphcdt), 2,6-dimethylmorpholinecarbodithioate (2,6-M2Morphcdt), 2,5-dimethylpyrrolecarbodithioate (2,5-M2Pyrrcdt)] and Fe2[2-MPipz(cdt)2]3 [(2-MPipz(cdt)2 = 2-methylpiperazine-l, 4-dicarbodithioate dianion)] have been synthesized. These compounds have been characterized by elemental analyses, infrared spectral and magnetic susceptibility measurements and in some cases by electron paramagnetic resonance studies. The room temperature magnetic moments of the complexes are indicative of a trigonally distorted octahedral geometry around iron(III) observing a 6A1 ↔ 2T2 spin croosover phenomenon. The EPR studies give the gav values 4.4960-4.9962.

Magnetic and spectroscopic characterization of copper(II) toluate adducts with substituted piperidines

New copper(II) toluate complexes with saturated monoheterocyclic bases, substituted piperidines, of the type Cu(OOCR)2L (where R = 2‐, 3‐, or 4‐CH3C6H4 and L = 1‐methyl‐, 1‐ethyl‐ or 2,6‐dimethylpiperidine) have been synthesized and characterized by elemental analyses, IR, electronic reflectance and EPR spectral and magnetic susceptibility measurement studies. All of these complexes show antiferromagnetic behaviour. The spin exchange parameter, − 2J, for three of these complexes has been evaluated from EPR measurements at different temperatures, which corresponds to axial binuclear copper(II) complexes with S = 1.

Bis(2,4–pentanedionato)vanadium(IV) aryloxides

Complexes of composition [VCl(acac)2(OAr1–4)] and [V(acac)2(OAr1–4)2] (HOAr1=HOC6H4NO2–4, HOAr2= HOC6H4OMe-4, HOAr3=HOC6H4But-4 and HOAr4= HOC6H2But-2,6–Me-4; acac=2,4–pentanedionato ion) have been synthesized by the reaction of [VCl2(acac)2] with the respective phenols or their trimethylsilyl derivatives. The complexes have been characterized by physicochemical and spectroscopic techniques. They are non-electrolytes in nitrobenzene. Room temperature magnetic moments in the 1.71–1.82μB range are consistent with the VIV system. The reactions of [VCl(acac)2(OAr2)] and [VCl(acac)2(OAr3)] with chloride acceptors have been studied by conductance techniques and the formation of ionic complexes of the types [V(acac)2(OAr2,3)][MCl4] (M=Fe, Al or Sb) and [V(acac)2(OAr2,3)][MCl6] (M=P or Sb) is indicated by the conductance composition curves. Several of these complexes have been isolated and characterized.

Magnetic and spectral studies on nickel(II) and copper(II) dithiocarbazates derived from isoniazid

Some isonicotinoyldithiocarbazate complexes of nickel(II) and copper(II), of general formulae M(IN-Dtcz)2, [M(IN-DtczH)2]Cl2, and [M(IN-DtczH-Sal)2]Cl2 (M = Ni(II), Cu(II); INDtcz = isonicotinoyldithiocarbazate; IN-DtczH = isonicotinoyldithiocarbazic acid; IN-DtczH-Sal = salicylaldehyde Schiff base of isonicotinoyldithiocarbazic acid), have been synthesized. These complexes have been investigated by elemental analyses, mass, room temperature infrared and electronic spectra, and variable temperature magnetic susceptibility measurements. The three nickel(II) dithiocarbazates and [Cu(IN-DtczH-Sal)2]Cl2 exhibit NS linkage of the ligands, while Cu(IN-Dtcz)2 and [Cu(IN-DtczH)2]Cl2 have ONS binding of the ligands. The nickel(II) dithiocarbazates have [NiN2S2] chromophore. Magnetic and solution electronic absorption spectral data reveal square-planar geometry for Ni(IN-Dtcz)2 and the existence of square-planar–tetrahedral equilibrium for [Ni(IN-DtczH)2]Cl2 and [Ni(IN-DtczH-Sal)2]Cl2. Copper(II) dithiocarbazates, namely Cu(IN-Dtcz)2, [Cu(IN-DtczH)2]Cl2, with ONS ligands having dimeric or polymeric octahedral structures, and [Cu(IN-DtczH-Sal)2]Cl2, with NS binding having dimeric square-planar structure, exhibit antiferromagnetism. Superexchange pathway involving the bridging nitrogen and sulfur of the isonicotinoyldithiocarbazate ligands rather than direct metal–metal exchange is suggested for antiferromagnetic interactions. The spin exchange parameter, −2J = 202.14 and 29.26 cm−1, has been evaluated for [Cu(IN-DtczH)2]Cl2 and [Cu(IN-DtczH-Sal)2]Cl2, respectively, while it could not be evaluated for Cu(IN-Dtcz)2 because the slope was negative due to the non-variation of its magnetic moment with temperature. The difference in antiferromagnetic behavior and inconsistency of 2J for [Cu(IN-DtczH-Sal)2]Cl2 has been attributed to different electronic and steric factors of the three ligands, that is, isonicotinoyldithiocarbazate, its acid, and salicylaldehyde Schiff-base derivative.

Synthesis and Studies on Nickel(III) and Copper(III) Complexes of 3-Methyl-, 4-Methyl- And 2,6-Dimethylpiperidine Carbodithioates

Abstract New complexes of trivalent nickel and copper, viz. Ni(III)(Lcdt)2X (X = Br, I and Lcdt = 4-methylpiperidinecarbodithioate anion (4-MePipdcdt) and 2, 6-dimethylpiperidinecarbodithioate anion (2, 6-Me2Pipdcdt) and Cu(III)(Lcdt)nXm (n = 2, m =1 when X = I and n = 1, m = 2 when X = Br and Lcdt = the anions: 3-methylpiperidinecarbodithioate (3-MePipdcdt), 4-MePipdcdt and 2, 6-Me2Pipdcdt have been prepared by oxidation of M(Lcdt)2 (M = Ni(II) and Cu(II)) with halogen X2 in suitable media. The complexes have been characterised by elemental analyses, infrared and electronic spectral and room-temperature magnetic susceptibility studies. For nickel(III) carbodithioates either a square-planar or square-pyramidal structure has been assigned and for the copper(III) carbodithioates, the presence of a mixture of singlet (S = 0) and triplet (S = 1) forms of square-planar species has been proposed.

4-Methylpiperazine-1-Carbodithioate Complexes of Iron(IV), Cobalt(IV) and Nicke(III) With Tetrachloroferrate as Anion

Abstract Complexes of the type M(4-MPipzcdt)nFeCl4 (M = Fe(IV), Co(IV) when n = 3; and M = Ni(III) when n = 2 and 4-MPipzcdt = 4-methylpiperazine-l-carbodithioate, have been obtained by oxidation of M(4-MPipzcdt)n (M = Fe(III), Co(III) when n = 3; and M = Ni(II) when n = 2) with anhydrous iron(III) chloride. They have been characterized by elemental analyses, room temperature infrared and electronic spectral and magnetic susceptibility measurements. The results of the magnetic and spectral studies suggest that the iron(IV) and cobalt(IV) complexes in octahedral geometries are low-spin species while the nickel(III) complex exhibits a low-spin, square-planar geometry. In all three complexes, however, the iron(III) ion (of the FeCl4 anion) in hexa-coordination is assumed to exhibit a high-spin low-spin equilibrium phenomenon.

Anomalous magnetic behaviour of nitrosylbis(carbodithioato)iron(I) compounds

Abstract Five compounds of the general formula Fe(NO)(L)n (n = 2, L = 4-methylpiperazine-l-carbodithioate, 4-phenylpiperazine-l-carbodithioate, thiomorpholine-N-carbodithioate, piperidine-N-carbodithioate; n = 1, L = 2-methylpiperazine-1,4-dicarbodithioate) have been prepared and characterized by elemental analyses, IR spectral studies and room- and liquid-nitrogen-temperature magnetic susceptibility measurements. Two of these complexes have also been subjected to variable-temperature magnetic susceptibility measurements. The temperature dependence of μeff has been correlated with a S = 3 2 ← S = 1 2 spin-crossover phenomenon.

Oxovanadium(IV), manganese(II) and manganese(III) carbodithioates exhibiting abnormal magnetic behaviour

SummaryNew carbodithioate complexes of the oxovanadium(IV), manganese(II) and manganese(III) ions have been prepared and studied by i.r. and electronic spectral and variable temperature magnetic susceptibility (77K to room temperature) measurements. The carbodithioate ligands, 4-methylpiperazine-1-carbodithioate (4-MPipzcdt) and 4-phenylpiperazine-1-carbodithioate (4-PPipzcdt), were derived from heterocyclic secondary amines. The VO(4-MPipzcdt)2 and VO(4-PPipzcdt)2 complexes possess C4v symmetry; Mn(4-PPipzcdt)2 is tetrahedral and Mn(4-PPipzcdt)3 is octahedral. All exhibit abnormal room temperature magnetic moments and the variable temperature magnetic moments suggest antiferromagnetism for the oxovanadium(IV) and the manganese(II) complexes and the occurrence of low spin (3T1g) ⇌high spin (5Eg) equilibrium in addition to antiferromagnetic interactions in the manganese(III) complex. The spin-spin exchange parameter (-2J) value for the VO(4-MPipzcdt)2 complex has been calculated using variable temperature magnetic susceptibility data.