The Extractive-Spectrophotometric Determination of Iron(III) As a Mixed-Ligand Complex with N-Hydroxy-N,N′DI-p-Tolyl-p-Toluamidine and Thiocyanate

The extractive-photometric determination or iron(III) as a mixed-ligand complex with N -hydroxy-N, N′ -di-p -tolyl-p -toluamidine (HDTTA) and thiocyanate is described. The orange-red Waterinsoluble 1:1:2 (metal: HDTTA: SCN^?) ternary complex formed in 0.1–0.6 M hydrochloric acid solutions is quantitatively extractable into benzene. The wavelength of maximum absorption, molar absorptivity and sensitivity of the colour system are 460nm, 12000 l. mole^?1 cm^?1 and 0.0046 μg Fe/cm ²respectively. The influence or foreign ions on the determination of iron has been studied. This method has also been applied to determine the iron content of several alloys.     

Ruthenium(III)-Phthalocyanine: Darstelllung und Eigenschaften von Di(halogeno)phthalocyaninato(1−)ruthenium(III), [Ru(X)2Pc] (X = Cl,Br, I)

Ruthenium(III) Phthalocyanines: Synthesis and Properties of Di(halo)phthalocyaninato(1?)ruthenium(III) Di(halo)phthalocyaninato(1?)ruthenium(III), [Ru(X)₂Pc^?] (X = Cl, Br, I) is prepared by oxidation of [Ru(X)₂Pc^2?]^? (Cl, Br, OH) with halogene in dichloromethane. The magnetic moment of [Ru(X)₂Pc^?] is 2,48 μ_B (X = Cl) resp. 2,56 μ_B (X = Br) in accordance with a systeme of two independent spins (low spin Ru^III and Pc^?: S = 1/2). The optical spectra of the red violet solution of [Ru(X)₂Pc^?] (Cl, Br) are typical for the Pc^? ligand with the “B” at 13.5 kK, “Q₁” at 19.3 kK and “Q₂ region” at 31.9 kK. Sytematic spectral changes within the iron group are discussed. The presence of the Pc^? ligand is confirmed by the vibrational spectra, too. Characteristic are the metal dependent bands in the m.i.r. spectra at 1 352 and 1 458 cm^?1 and the strong Raman line at 1 600 cm^?1. The antisymmetric Ru? X stretch (v_as(Ru? X)) is observed at 189 cm^?1 (X = I) resp. 234 cm^?1 (X = Br). There are two interdependent bands at 295 and 327 cm^?1 in the region expected for v_as(Ru? Cl) attributed to strong interaction of v_as(Ru? Cl) with an out-of-plane Pc^? tilting mode of the same irreducible representation. Only the symmetric Ru? Br stretch at 183 cm^?1 is selectively enhanced in the resonance-Raman(RR) spectra. The Raman line at 168 cm^?1 of the diiodo complex is assigned to loosely bound iodine. The broad band at 978 cm^?1 in the RR spectra of the dichloro complex is due to an intraconfigurational transition within the electronic ground state of low spin Ru^III split by spin orbit coupling.     

Effect of Inter‐Porphyrin Distance on Spin‐State in Diiron(III) μ‐Hydroxo Bisporphyrins

The synthesis, structure, and properties of bischloro, μ‐oxo, and a family of μ‐hydroxo complexes (with BF₄^?, SbF₆^?, and PF₆^? counteranions) of diethylpyrrole‐bridged diiron(III) bisporphyrins are reported. Spectroscopic characterization has revealed that the iron centers of the bischloro and μ‐oxo complexes are in the high‐spin state (S=⁵/₂). However, the two iron centers in the diiron(III) μ‐hydroxo complexes are equivalent with high spin (S=⁵/₂) in the solid state and an intermediate‐spin state (S=³/₂) in solution. The molecules have been compared with previously known diiron(III) μ‐hydroxo complexes of ethane‐bridged bisporphyrin, in which two different spin states of iron were stabilized under the influence of counteranions. The dimanganese(III) analogues were also synthesized and spectroscopically characterized. A comparison of the X‐ray structural parameters between diethylpyrrole and ethane‐bridged μ‐hydroxo bisporphyrins suggest an increased separation, and hence, less interactions between the two heme units of the former. As a result, unlike the ethane‐bridged μ‐hydroxo complex, both iron centers become equivalent in the diethylpyrrole‐bridged complex and their spin state remains unresponsive to the change in counteranion. The iron(III) centers of the diethylpyrrole‐bridged diiron(III) μ‐oxo bisporphyrin undergo very strong antiferromagnetic interactions (J=?137.7 cm^?1), although the coupling constant is reduced to only a weak value in the μ‐hydroxo complexes (J=?42.2, ?44.1, and ?42.4 cm^?1 for the BF₄, SbF₆, and PF₆ complexes, respectively).     

The structure and magnetic properties of μ3-oxotriiron(III) complex [Fe3O(OBz)6(CH3OH)3](NO3)(CH3OH)2

A new μ₃-O triiron(III) complex [Fe₃O(OBz)₆(CH₃OH)₃](NO₃)(CH₃OH)₂ (HOBZ = benzoic acid) has been synthesized, its structure has been determined and variable temperature magnetic susceptility has also been measured. In the molecule, three iron atoms formed an equilateral triangle with μ₃-O in center. The fitting to the magnetic susceptibility showed that an intramolecular antiferromagnetic exchange interaction occurred between iron atoms with J=-25.51 cm^?1, and a weaker intermolecular autiferromagnetic exchange interaction occurred with zJ' = ?2.30 cm^?1.     

Zero-Order and Third-Derivative Spectrophotometric Determination of Iron(III) with 4-(2-Pyridylazo)-Resorcinol in the Presence of N-Hexadecylpyridinium Chloride

Abstract

The complex formation reaction between iron(III) and 4-(2-pyridylazo) resorcinol(PAR) in the presence of various water soluble surfactants((N-hexadecylpyridinium chloride (HPC), poly(vinylalcohol)(PVA), sodium dodecylsulfate(SDS), sodium N-lauroylsarcosine(SL)) alone or in combination at weakly acidic media was systematically investigated. An improved and more sensitive spectrophotometric method for the determination of iron was proposed by zero-order and third-derivative spectrophotometry using the PAR-iron(III)-HPC ternary complex system at about pH 5.2. The calibration curve was rectilinear in the ranges of 0 – 15.0 μg iron(III) in a final 10-ml on the zero-order spectrophotometry. Also, upon the third-derivative spectrophotometry, Beer's law was obeyed in the range of 0 – 8.0 μg iron(III)/10 ml by measuring the distance between the absorbance peak(λ₁ = 527 nm) and the valley (λ₂ = 560 nm). The apparent molar absorptivity was 4.8 × 10⁴ 1 mol^?1 cm^?1 in zero-order spectrophotometry, and 1.36 × 10⁵ mol^?1 cm^?1 in third-derivative spectrophotometry. The effect of foreign ions was decreased within ½ – ¼-fold in comparison with the method in the presence of PVA without HPC. Especially, the third-derivative spectrophotometric method was sensitive and selective, and made possible to assay mixed sample solution containing iron(III) and copper(II), etc.     

Spectrophotometric determination of iron(III) with EDTA tetrahydrazide

The tetrahydrazide of ethylenediamine tetraacetic acid (NH₂NH)₄-EDTA was synthesized from the EDTA ester and hydrazine hydrate in ethanolic solution, the resulting (NH₂NH)₄-EDTA being recrystallized in 60% ethanol. When the spectrophotometric study of the iron(III) (NH₂NH)₄-EDTA complex in aqueous solution was made two absorption maxima at 530 and 450 nm at pH 4.5 and 11.0, respectively, were found. Beer's law is obeyed in the range 1.0–20.0 μg Fe(III) ml^?1 at 530 nm and pH 4.5 and 0.5–12.0 μg Fe(III) ml^?1 at 450 nm and pH 11.0, the molar absorptivities being 1.95 × 10³ 1 mol^?1 cm^?1 at 530 nm and 3.35 × 10³ 1 mol^?1 cm^?1 at 450 nm, respectively. The Ringbom optimal interval falls between about 3 and 18 μg Fe(III) ml^?1 at 530 nm and about 2–14 μg Fe(III) ml^?1 at 450 nm. The reaction between the metal and the ligand was also investigated. The method has been successfully applied to the determination of iron in talcs.     

Darstellung,Eigenschaften und elektronische Raman-Spektren von Bis(chloro)phthalocyaninatoferrat(III), -ruthenat(III) und -osmat(III)

Preparation, Properties and Electronic Raman Spectra of Bis(chloro)-phthalocyaninatoferrate(III), -ruthenate(III) and -osmate(III) Bis(chloro)phthalocyaninatometalates of Fe^III, Ru^III and Os^III [MCl₂Pc(2-)]^?, with an electronic low spin ground state are formed by the reaction of [FeClPc(2-)] resp. H[MX₂Pc(2?)] (M = Ru, Os; X = Cl, I) with excess chloride in weakly coordinating solvents (DMF, THF) and are isolated as (n-Bu₄N) salts. The asym. M? Cl stretch (ν_as(MCl)) is observed in the f.i.r. at 288 cm^?1 (Fe), 295 cm^?1 (Ru), 298 cm^?1 (Os), ν_as(MN) at 330 cm^?1 (Fe), 327 cm^?1 (Ru), and 317 cm^?1 (Os); only ν_s(OsCl) at 311 cm^?1 is resonance Raman (r.r.) enhanced with blue excitation. The m.i.r. and FT-Raman spectra are typical for hexacoordinated phthalocyanines of tervalent metal ions. The UV-vis spectra show besides the characteristic π-π* transitions (B, Q, N, L band) of the Pc ligand a number of extra bands at 12–15 kK and 18–24 kK due to trip-doublet and (Pc→M)CT transitions. The effect of metal substitution is discussed. The r.r. spectra obtained by excitation between the B and Q band (λ₀ = 476.5 nm) are dominated by the intraconfigurational transition Γ₇ Γ ₈ arrising from the spin-orbit splitting of the electronic ground state for Fe^III at 536 cm^?1, for Ru^III at 961 cm^?1 and Os^III at 3 028 cm^?1. Thus the spin-orbit coupling constant increases very greatly down the iron group: Fe^III (357 cm^?1)< Ru^III (641 cm^?1)< Os^III (2 019 cm^?1). The Γ₇ Γ ₈-transition is followed by a very pronounced vibrational finestructure being composed in the r.r. spectra by the coupling with ν_s(MCl), δ(MClN) and the most intense fundamental vibrations of the Pc ligand. In absorption only vibronically induced transitions are observed for the Ru and Os complex at 1 700-2800 rsp. 3100-5800 em^?1 instead of the 0-0 phonon transitions. The most intense lines are attributed to combinations of the intense odd vibrational mo-des at ≈ 740 and 1120 cm^?1 with ν₅(MCI), δ(MClN).     

Spectrophotometric Determination of Diphenadione Via its Metal Complexes

Abstract

Spectrophotometric procedure is described for the quantitative determination of diphenadione [2-(diphenylacetyl)-1,3-indandione], based on direct spectrophotometric measurements of the absorbances of its iron (III), iron (II) and cobalt (II), metal complexes at 488 nm, 505 nm and (334 nm, 372 nm), respectively. The drug reacts with metals in the ratio of 3:1 and 2:1 for iron (III) and for both iron (II) and cobalt (II) respectively. The obtained complexes have apparent molar absorptivities of 1.48 × 10³ 1 mol^?1 cm^?1, 0.714 × 10³ 1 mol^?1cm^?1 and (1.70 × 10³ 1 mol^?1cm^?1, 1.93 × 10³ 1 mol^?1cm^?1) for iron (III), iron (II) and cobalt (II) complexes, respectively. The procedure is suggested for the determination of 51–400 μg.ml^?1 diphenadione via the iron (II) complex and 35–170 μg.ml^?1 diphenadione via both cobalt (II) and iron (III) complexes. The suggested procedure has accuracies of 99.79 ± 0.67%, 99.64 ± 0.37% and (100.09 ± 0.53%, 99.99 ± 0.42%) for the metal complexes of iron (III), iron (II) and cobalt (II), respectively.     

Slow Magnetic Relaxation from Hard‐Axis Metal Ions in Tetranuclear Single‐Molecule Magnets

We report the synthesis of the novel heterometallic complex [Fe₃Cr(L)₂(dpm)₆]?Et₂O ( Fe₃CrPh ) (Hdpm=dipivaloylmethane, H₃L=2‐hydroxymethyl‐2‐phenylpropane‐1,3‐diol), obtained by replacing the central iron(III) atom by a chromium(III) ion in an Fe₄ propeller‐like single‐molecule magnet (SMM). Structural and analytical data, high‐frequency EPR (HF‐EPR) and magnetic studies indicate that the compound is a solid solution of chromium‐centred Fe₃Cr (S=6) and Fe₄ (S=5) species in an 84:16 ratio. Although SMM behaviour is retained, the |D| parameter is considerably reduced as compared with the corresponding tetra‐iron(III) propeller (D=?0.179 vs. ?0.418 cm^?1), and results in a lower energy barrier for magnetisation reversal (U_eff/k_B=7.0 vs. 15.6 K). The origin of magnetic anisotropy in Fe₃CrPh has been fully elucidated by preparing its Cr‐ and Fe‐doped Ga₄ analogues, which contain chromium(III) in the central position (c) and iron(III) in two magnetically distinct peripheral sites (p1 and p2). According to HF‐EPR spectra, the Cr and Fe dopants have hard‐axis anisotropies with D_c=0.470(5) cm^?1, E_c=0.029(1) cm^?1, D_p1=0.710(5) cm^?1, E_p1=0.077(3) cm^?1, D_p2=0.602(5) cm^?1, and E_p2=0.101(3) cm^?1. Inspection of projection coefficients shows that contributions from dipolar interactions and from the central chromium(III) ion cancel out almost exactly. As a consequence, the easy‐axis anisotropy of Fe₃CrPh is entirely due to the peripheral, hard‐axis‐type iron(III) ions, the anisotropy tensors of which are necessarily orthogonal to the threefold molecular axis. A similar contribution from peripheral ions is expected to rule the magnetic anisotropy in the tetra‐iron(III) complexes currently under investigation in the field of molecular spintronics.     

Studies on the magnetic property of μ3-oxotriiron(III) complex [Fe3O(OBz)6(CH3OH)3](NO3)(CH3OH)2 (HOBz?Benzoic acid)

The magnetic property of μ₃-oxotriiron(III) complex [Fe₃O(OBz)₆(CH₃OH)₃](NP₃)-(CH₃OH)₂ (HOBz? benzoic acid) has been studied. We use isosceles triangle model and molecular field correction to fit the experimental magnetic susceptibility data. It shows that an intramolecular antiferromagnetic exchange interaction occurs with J = -31.27 cm^?1, J'= -27.26 cm^?1, and a weaker intermolecular antiferromagnetic exchange interaction occurs with zJ' = - 3.76 cm^?1. We give the d⁵-d⁵-d⁵ energy level diagram of triiron(III) complex as a function of J'/J. From the diagram we can get the total spin ST of the complex as 1/2 in the ground state.     

Spectrophotometric Determination of Iron In Wines,Vegetables, Pharmaceutical Compounds and Minerals With Mandelohydroxamic Acid (Mha)

Abstract

A new reagent, mandelohydroxamic acid (MHA), which has an easy synthesis and an high water solubility (64.48 gL^?1) is proposed for a simple, rapid, selective and sensitive method for the spectrophotometric determination of iron based upon the formation of the MHA-Fe(III) complex and its extraction into n-butanol under optimum operating conditions. A yellow color is formed when the complex is extracted from acidic aqueous medium (Vw/Vo[dbnd]5) in the organic solvent (apparent molar absortivity 1.15 10⁴ L mol^?1 cm^?1 at a wavenlength of 430 nm). the relative error is 0.5% (2 ppm of iron) and the detection limit is 0.05 g mL^?1 of Fe(III). the method has been applied to the determination of iron in wines, vegetables, pharmaceutical compounds and minerals.     

Spectrophotometric determination of chloride in non-polar media by the mercury(II) thiocyanate reaction

A simple, rapid and accurate method for the spectrophotometric determination of chloride in non-polar media is described. The method is based on the well-known reaction of mercury(II) thiocyanate with chloride to release thiocyanate, which then reacts with iron(III). The optimum concentrations of reagents for the determination of chloride in 2,2,4-trimethylpentane (iso-octane) and cyclohexane are reported. The molar absorptivity of the complex at 505 nm is 5120 ± 200 dm³ mol^?1 cm^?1 for iso-octane and 5340 ± 340 dm³ mol^?1 cm^?1 for cyclohexane. Beer's Law is obeyed in the range 2 × 10^?7–2 × 10^?5 mol dm^?3 (0.01–1 mg l^?1) chloride.     

Stepwise magnetic behavior of the liquid crystal iron(III) complex

EPR and Mössbauer spectroscopy is used to study a new liquid crystal complex of iron(III) with a Schiff base: 4,4′-dodecyloxybenzoyloxybenzoyl-4-oxysalicylidene-2-aminopyridine with a PF ₆ ^? counterion. It is shown that Fe(III) ions exist only in the high-spin (HS, S = 5/2) state. It is found that under the influence of temperature the system demonstrates the stepwise behavior of the product of the integrated intensity of EPR lines (I) and temperature (proportional to χ T, where χ is the magnetic susceptibility) with an inflection point at ～80 K. Above 80 K a new EPR spectrum is detected due to the excited S = 2 state and the formation of dimeric molecules (through oxygen bridges) with a strong intramolecular antiferromagnetic exchange interaction J ₁ = 162.1 cm^?1. Below 80 K iron(III) complexes are organized in 1D chains where the exchange value J ₂ = 2.1 cm^?1. At 80 K there is a structural phase transition in the system: the transition from a 1D chain organization of HS Fe(III) centers to dimeric molecules. Based on quantum chemical calculations a model of the binuclear iron(III) complex is proposed.     

Spectroscopic study of 2,3-Bis(p-methoxybenzoyl)cyclopentadiene as potential iron(III)-chelating agent

2,3-Bis(p-methoxybenzoyl)cyclopentadiene was studied as iron(III)-chelating agent. Its pK _a value was determined by spectrophotometry (pK _a = 8.27 ± 0.02 at 25 ± 0.1°C; λ = 421 nm). 2,3-Bis(p-methoxybenzoyl)cyclopentadiene reacts with Fe³⁺ ions in aqueous ethanol (1:1, by volume) to give a 2:1 ligandmetal complex. The effects of different factors on the complex formation were studied. The reaction of 2,3-bis(p-methoxybenzoyl)cyclopentadiene with Fe³⁺ ions can be used as an alternative method for spectrophotometric determination of iron(III) in a range of concentrations from 0.1 to 1 μg cm⁻³, where the Beer law is fulfilled with a correlation coefficient of 0.9992. The results of spectrophotometric determination of iron(III) in geological materials (iron rock) showed very good agreement with those obtained by the atomic absorption measurements. Published in Russian in Zhurnal Obshchei Khimii, 2006, Vol. 76, No. 5, pp. 790–793. The text was submitted by the authors in English.     

Complex Formation Equilibria of Iron(III) With 2-Hydroxy-3- Pyridinol and 2-Mercapto-3-Pyridinol. Spectrophotometry Determination of Iron(III) In Multivitamins

ABSTRACT

The complex equilibria of iron(III) with 2-hydroxy-3-pyridinol (HHP), and 2-mercapto-3-pyridinol (MHP) were studied spectrophotometrically in 40% (v/v) ethanol and an ionic strength of 0.1M (NaCIO₄). The complexation reactions were demonstrated and characterized using graphical logarithmic analysis of the absorbance pH-graphs. After considering all the different parameters a simple, rapid, sensitive and selective method for spectrophotometric determination of trace levels of iron(III) was proposed based on the formation of (Fe -MHP) complex at pH 2.5 (λ_max = 640 nm, ? = l×10⁴ L mol^?1 cm^?). The interference of a large number of foreign ions was investigated. The method has been applied successfully for the determination of iron content in some multivitamins with mineral preparations and infant milk products.     

Voltammetry of Dissolved Iron(III)–Nitrilotriacetate–Hydroxide System in Water Solution

The investigation of the dissolved iron(III)–nitrilotriacetate–hydroxide system in the water solution (I=0.1 mol L^?1 in NaClO₄; pH 8.0±0.1) using differential pulse cathodic voltammetry, cyclic voltammetry, and sampled direct current (DC) polarography, was carried out on a static mercury drop electrode (SMDE). The dissolved iron(III) ion concentrations varied from 2.68×10^?6 to 6×10^?4 mol L^?1 and nitrilotriacetate concentrations were 1×10^?4 and 5×10^?4 mol L^?1. By deconvoluting of the overlapped reduction voltammetric peaks using Fourier transformation, four relatively stable, dissolved iron(III) complex species were characterized, as follows: [Fe(NTA)₂]^3?, mixed ligand complexes [FeOHNTA]^? and [Fe(OH)₂NTA]^2?, showing a one‐electron quasireversible reduction, and binuclear diiron(III) complex [NTAFeOFeNTA]^2?, detected above 4×10^?4 mol L^?1 of the added iron(III) ions, showing a one‐electron irreversible reduction character. The calculations with the constants from the literature were done and compared with the potential shifts of the voltammetric peaks. Fitting was obtained by changing the following literature constants: log β₂([Fe(NTA)₂]^3?) from 24 to 27.2, log β₁([FeNTA]^?) from 8.9 to 9.2, log β₂([Fe(NTA)₂]^4?) from 11.89 to 15.7 and log β₂([Fe(OH)₂NTA]^3?) from 15.63 to 19. The determination of the electrochemical parameters of the mixed ligand complex [FeOHNTA]^?, such as: transfer coefficient (α), rate constant (k_s) and formal potential (E°') was done using a sampled DC polarography, and found to be 0.46±0.05, 1.0±0.3×10^?3 cm s^?1, and ?0.154±0.010 V, respectively. Although known previously in the literature, these four species have now for the first time been recorded simultaneously, i.e. proved to exist simultaneously under the given conditions.     

Spin-crossover phenomena in tris(trifluoronicotinoylacetonato) iron (III)

Tris(trifluoronicotinoylacetonato) iron(III) has been shown to exhibit spin-crossover phenomenon between ⁶A_1g and ²T_2g terms which are about 322 cm^?1 apart.     

Photometric determination of iron (III)

A sensitive colored reaction of tiron with iron (III) is described. It is based on a complex formation between tiron and iron (III) in basic medium. The method is suitable to determine 0.4–10 ppm of iron (III) with a relative standard deviation of 0.45–1.4% depending on the concentration level, molar absorptivity of 5.7 × 10³ liter mol⁻¹ cm⁻¹, and Sandell sensitivity index of 0.0098 μg/cm².Because of being simple and rapid, this method can certainly be used in routine analysis.     

Monomere und dimere Chrom(III)-Phthalocyanine: Synthese und Eigenschaften von Hydroxopyridinophthalocyaninatochrom(III) und μ-Oxodi(pyridinophthalocyaninatochrom(III))

Monomeric and Dimeric Chromium(III) Phthalocyanines: Synthesis and Properties of Hydroxopyridinophthalocyaninatochromium(III) and μ-Oxodi(pyridinophthalocyaninatochromium(III)) Heating of ?[Cr(OH)Pc^2?]”? in pyridine (Py) gives the paramagnetic (T = 273 K) complexes [Cr(OH)(Py)Pc^2?] (μ_Cr = 3.84 μ_B) and [(Cr(Py)Pc^2?)₂O] (μ_Cr = 1.24 μ_B) by consecutive substitution and condensation reactions. The UV-VIS spectra are characterized by the typical B, Q, and N regions of the Pc^2? ligand being shifted hypsochromically for the dimer with respect to the monomer due to excitonic coupling (1.5 kK). Regions of weak absorbance between 8 and 13 resp. 19 kK are assigned to trip-quartet transitions for both complexes. A weak band at 870 cm^?1 in the FIR/MIR spectra is assigned to v_as(Cr? O? Cr). In the resonance Raman(RR) spectra v(Cr? O) at 514 cm^?1 resp. v_s(Cr? O? Cr) at 426 cm^?1 is selectively enhanced. Further strong RR-lines of the μ-Oxo dimer at 110 and 631 cm^?1 are assigned to a (Py? Cr? O)- resp. internal pyridine deformation of a_1g symmetry. An assignment as 2v_as(Cr? O? Cr) is proposed for the remarkable RR line at 1740 cm^?1.     

Preparation and Properties of trans-[CoCl2(tmd>)2]Cl,and trans- and cis-[Co(NCS)2(tmd)2]NO3 (tmd: Tetramethylenediamine)

The cobalt(III) complexes [CoX₂(tmd)₂]⁺ (X: Cl^? or NCS^?, tmd: tetramethylenediamine), in which tmd forms a seven-membered chelate ring, have been prepared. Trans-[CoCl₂(tmd)₂]Cl was derived from [Co(NO₂)₂(tmd)₂]NO₃ in a fairly good yield. Two geometrical isomers, trans and cis, of [Co(NCS)₂-(tmd)₂]NO₃ were independently synthesized from trans-[CoCl₂(tmd)₂]Cl by different methods. The geometrical configurations of the isomeric pair of the NCS complex have been determined based on chromatographic behavior, electronic absorption spectra, and vibrational spectra. The d-d and CT absorption maxima of the NCS complex (18.7 x 10³cm^?1 (ε = 275) and 30.9 x 10³cm^?1 (ε = 3630) for the trans isomer, 19.3 x 10³cm^?1 (ε = 302) and 31.0 x 10³cm^?1 (ε = 4070) for the cis isomer) and the Co-N(amine) stretching frequency of trans-[CoCl₂(tmd)₂]Cl (418 cm^?1) have been compared with those of the corresponding ethylenediamine and trimethylenediamine complexes.