Structural characterization of five-coordinate copper(II), nickel(II), and cobalt(II) thiocyanato complexes derived from bis(2-(3,5-dimethyl-1-pyrazolyl)ethyl)amine

The reaction of M(ClO₄)₂·6H₂O with NH₄NCS in presence of the organic sterically hindered bis(2-(di-3,5-dimethyl-1-pyrazolyl)ethyl)amine (bedmpza) afforded the five-coordinate mononuclear dithiocyanato-M(II) complexes [M(bedmpza)(NCS)₂]·xMeOH (1: M = Cu²⁺, x = 0; 2: M = Ni²⁺, x = 0; 3: M = Co²⁺, x = 0.84). The compounds which proved to be non-electrolytes were characterized by IR and UV-Vis spectroscopy and their molecular structures were determined by single-crystal X-ray crystallography. In these complexes, the five-coordinate geometry was achieved by the three N-donors of the ligand bedmpza and two N atoms of the terminal thiocyanato ligands. The Cu(II) complex exists in two polymorphs 1-I and 1-II: an intermediate five-coordinate geometry with the two thiocyanato ligands are arranged as cisoid in 1-I and distorted square pyramidal geometry with the thiocyanato ligands are in transoid orientation in 1-II. Although the later geometry was also observed in the nickel complex 2, distorted trigonal bipyramidal geometry was found in 3. Each complex forms hydrogen bonds of type N-H?S from the secondary amine N(3) donor atoms to the adjacent terminal S(1) acceptor atoms of the thiocyanate group. The thermal behavior of the two polymorphs 1-I and 1-II were similar and no significant differences were observed between the two complexes.     

Ruthenium(III) complexes of amine-bis(phenolate) ligands as catalysts for transfer hydrogenation of ketones

Twelve ruthenium(III) complexes bearing amine-bis(phenolate) tripodal ligands of general formula [Ru(L¹–L³)(X)(EPh₃)₂] (where L¹–L³ are dianionic tridentate chelator) have been synthesized by the reaction of ruthenium(III) precursors [RuX₃(EPh₃)₃] (where E = P, X = Cl; E = As, X = Cl or Br) and [RuBr₃(PPh₃)₂(CH₃OH)] with the tripodal tridentate ligands H₂L¹, H₂L² and H₂L³ in benzene in 1:1 molar ratio. The newly synthesized complexes have been characterized by analytical (elemental and magnetic susceptibility) and spectral methods. The complexes are one electron paramagnetic (low-spin, d⁵) in nature. The EPR spectra of the powdered samples at RT and the liquid samples at LNT shows the presence of three different ‘g’ values (g_x ≠ g_y ≠ g_z) indicate a rhombic distortion around the ruthenium ion. The redox potentials indicate that all the complexes undergo one electron transfer process. The catalytic activity of one of the complexes [Ru(pcr-chx)Br(AsPh₃)₂] was examined in the transfer hydrogenation of ketones and was found to be efficient with conversion up to 99% in the presence of isopropanol/KOH.     

Cu(II) and Pd(II) complexes of N-(2-hydroxybenzyl)aminopyridines

N-(2-Hydroxybenzyl)aminopyridines (Lⁱ) react with Cu(II) and Pd(II) ions to form complexes in the compositions Cu(Lⁱ)₂(CH₃COO)₂ · nH₂O (n = 0, 2, 4), Pd(Lⁱ)₂Cl₂ · nC₂H₅OH (n = 0, 2) and Pd(L²)₂Cl₂ · 2H₂O. In the complexes, the ligands are neutral and monodentate which coordinate through pyridinic nitrogen. Crystal data of the complexes obtained from 2-amino pyridine derivative have pointed such a coordinating route and comparison of the spectral data suggests the validity of similar complexation modes of other analog ligands. Cu(II) complex of N-(2-hydroxybenzyl)-2-aminopyridine (L¹), [Cu(L¹)₂(CH₃COO)₂] has slightly distorted square planar cis-mononuclear structure which is built by two oxygen atoms of two monodentate carboxylic groups disposed in cis-position and two nitrogen atoms of two pyridine rings. The remaining two oxygen atoms of two carboxylic groups form two Cu and H bridges containing cycles which joint at same four coordinated copper(II) ion. IR and electronic spectral data and the magnetic moments as well as the thermogravimetric analyses also specify on mononuclear octahedric structure of complexes [Cu(L²)₂(CH₃COO)₂ · 2H₂O] and [Cu(L³)₂(CH₃COO)₂ · 4H₂O] where L² and L³ are N-(2-hydroxybenzyl)-2- or 3-aminopyridines, respectively.     

Evaluation of 1-methyl-3,4-hydroxypyridinecarboxylic acids as possible bidentate chelating agents for iron(III): Metal–ligand solution chemistry

The chemical interactions of 1-methyl-3-hydroxy-4-pyridinecarboxylic acid (1M3H4P) and 1-methyl-4-hydroxy-3-pyridinecarboxylic acid (1M4H3P) with Fe(III) were investigated in aqueous 0.6 m (Na)Cl at 25 °C by means of potentiometric titrations and UV–Vis spectrophotometry. A large number of complexes were formed in solution with stoichiometry FeL_xH_y, x = 1, 2, 3 and y = 0, −1, −2. In view of a possible application to Fe(III) chelation therapy, the efficiencies of the ligands to chelate the metal ion were evaluated in vitro at physiological pH. 1M3H4P and 1M4H3P show a lower complexation efficiency with Fe(III) than that of other available chelators, but higher than that of their non-methylated analogs 3H4P and 4H3P.     

Synthesis of the first examples of stable heterometallic isopropoxides of an organometallic RSn(IV) moiety

Five-, six-, and seven-coordinate volatile butyltin(IV) heterobimetallic derivatives, respectively of the types, [BuSn{(μ-OPrⁱ)₂Al(OPrⁱ)₂}Cl₂] (1), [BuSn{(μ-OPrⁱ)₂Al(OPrⁱ)₂}₂Cl] (2), and BuSn{(μ-OPrⁱ)₂M(OPrⁱ)_x − 2}₃ (3:M = Al (x = 4); 4:M = Ga (x = 4); 5:M = Nb (x = 6)) have been synthesized by the reactions of BuSnCl₃ with potassium tetraisopropoxoaluminate in 1:1, 1:2, and 1:3 molar ratios. Replacement reactions of chloride in (1) and (2) with appropriate alkoxometallate (tetraisopropoxoaluminate, tetraisopropoxogallate, or hexaisopropoxoniobate) ligands result in the formation of novel BuSn(IV) heterotri- and tetra-metallic derivatives. All of these derivatives have been characterized by elemental analyses, molecular weight measurements, and spectroscopic (IR, ¹H, ²⁷Al, and ¹¹⁹Sn NMR) studies. Based on these studies, plausible structures for the new derivatives involving bidentate ligation of the alkoxometallate ligands have been suggested.     

Ferromagnetic exchange coupling in phosphonato-bridged dinuclear copper(II) compound with monoethyl (pyridyn-2-ylmethyl)phosphonate ligand (2-mpmpe): Cu2(2-mpmpe)2(H2O)2(NO3)2

The interaction of diethyl (pyridyn-2-ylmethyl)phosphonate (2-pmpe) with Cu(NO₃)₂ · 6H₂O leads to a partial hydrolysis of the starting ligand and formation of the compound of the formula Cu₂(2-mpmpe)₂(H₂O)₂(NO₃)₂, where 2-mpmpe = monoethyl (pyridyn-2-ylmethyl)phosphonate. The crystal and molecular structure of a copper(II) compound was determined by single X-ray diffraction method. Its structure consists of five-coordinated in distorted square planar geometry (CuNO₄ chromophore) copper(II) ions doubly bridged by OPO from phosphonate. The Cu?Cu distance is 4.69 Å. The crystal packing is determined by the interdinuclear hydrogen bond system, which leads to a three-dimensional (3D) H-bonds network. The compound was characterized by infrared, ligand field, EPR spectroscopy, and magnetic studies. The magnetic properties of the title compound investigated over the 1.8–300 K, revealed the occurrence of a weak ferromagnetic coupling through phosphonate bridge (J = 1.86 cm⁻¹) and interdimer superexchange coupling through H-bond network (zJ′ = −0.17 cm⁻¹). Spectroscopic and magnetic properties are presented in the light of crystal structure.     

Paramagnetic ruthenium(III) complexes bearing O,O chelating ligands: Synthesis, spectra, molecular structure and electron transfer properties

Paramagnetic Ru(III) complexes of the type [RuX₂(EPh₃)₂(L)] (where X = Cl or Br; E = P or As; L = monobasic bidentate benzophenone ligand) have been synthesized from the reaction of ruthenium(III) precursors, viz. [RuX₃(EPh₃)₃] (where X = Cl, E = P; X = Cl or Br, E = As) or [RuBr₃(PPh₃)₂(CH₃OH)] and substituted hydroxy benzophenones in a 1:1 molar ratio in benzene under reflux for 6 h. The hydroxy benzophenone ligands behave as monoanionic bidentate O,O donors and coordinate to ruthenium through the phenolate oxygen and ketonic oxygen atoms, generating a six-membered chelate ring. The compositions of the complexes have been established by analytical and spectral (FT-IR, UV-Vis, EPR) and X-ray crystallography methods. The single crystal structure of the complex [RuCl₂(PPh₃)₂(L₁)] (1) has been determined by X-ray crystallography and indicates the presence of a distorted octahedral geometry in these complexes. The magnetic moment values of the complexes are in the range 1.75-1.89 μ_B, which reveals the presence of one unpaired electron in the metal ion. EPR spectra of liquid samples at liquid nitrogen temperature (LNT) show a rhombic distortion (g_x ≠ g_y ≠ g_z) around the ruthenium ion. The complexes are redox active and display quasi-reversible oxidation and quasi-reversible reduction waves versus Ag/AgCl.     

Interaction of uranium(VI) with nitrogen containing model ligands studied by laser-induced fluorescence spectroscopy

The complexation of uranium(VI) with two nitrogen containing organic ligands, representing model substances for humic acid building blocks, has been investigated at pH values between 1.5 and 4.5 and an ionic strength of 0.1 M (NaClO₄). Using two independent fluorescence spectroscopic methods, time-resolved laser-induced fluorescence spectroscopy (TRLFS) and TRLFS with ultrafast pulses (fs-TRLFS), the complex formation of uranium(VI) with anthranilic and nicotinic acid in aqueous solution was studied. In both systems a decrease in the luminescence intensity was observed with increasing ligand or metal ion concentration. Uranium(VI) complexes of the type M_xL_yH_z were identified. Anthranilic acid forms a 1:1 complex under the given experimental conditions with a stability constant of log β₁₁₁ = 8.00 ± 0.31. For the uranium(VI) nicotinate system 1:1 and 1:2 complexes could be identified. The corresponding formation constants were calculated to be log β₁₁₁ = 8.59 ± 0.17 and log β₁₂₂ = 17.18 ± 0.35.     

In depth investigation of the synthesis, structural, and spectroscopic characterization of a high pH binary Co(II)-N,N-bis(phosphonomethyl)glycine species. Association with aqueous speciation studies of binary Co(II)-(carboxy)phosphonate systems

Cobalt is an abundant metal ion present in the abiotic and biological world. The chemical reactivity of Co(II) is exemplified through complex interactions with variable molecular mass ligands, including amino acids, peptides, variable nature organic ligands, and/or phospho(nate)-derivatives thereof. Poised to gain insight into the chemical reactivity of Co(II) toward the family of mixed (carboxy)phosphonate-containing ligands, pH-specific aqueous reactions were carried out between Co(II) and N,N-bis(phosphonomethyl)-glycine (NTA2P), leading to a new pH-structural variant species (NH₄)₃[Co(C₄H₆O₈NP₂)(H₂O)₂]·4H₂O (1) at pH 8. Compound 1 was characterized analytically, spectroscopically (FT-IR, UV-Vis, EPR), and magnetically. X-ray crystallography reveals a mononuclear complex of Co(II) in an NO₅ octahedral environment. The solid state magnetic and EPR data on 1 suggest the presence of a high-spin Co(II) in a distorted octahedral geometry, with a ground state of an effective spin S = 1/2. The solution UV-Vis and EPR data suggest retention of the integrity of 1, consistent with the magnetization measurements. Detailed aqueous speciation studies on binary Co(II)-carboxylate (NTA) and all Co(II)-(carboxy)phosphonate (NTA_xP; x = 1-3) systems reveal the aqueous distributions of all species involved in the respective systems and project a mononuclear species not unlike that of 1 in the Co(II)-NTA2P system. The structural and chemical attributes of the title complex reflect the (a) pH-dependent chemical reactivity in the binary Co(II)-NTA2P system, and (b) structure-activity correlations in the aqueous media linking both high and low pH-structural variants. To this end, fundamental structural properties influence the reactivity of Co(II) toward phosphonate and mixed carboxyphosphonate ligands and are ultimately exemplified as a function of phosphonate-containing moieties in NTA derivatives. The variably configured species in such binary Co(II)-ligand systems define the pH dependence and nature of interactions between the two reagents, and could serve further as precursors in the design and discovery of new Co(II)-organophosphonate materials of specific structural lattice, spectroscopic, and magnetic properties.     

Co(III) complexes of the type [(L)Co(O2CO)] (L = tripodal tetraamine ligand): Synthesis,structure, DFT calculations and Co NMR

The syntheses and characterisation of the Co(III) complexes [(L)Co(O₂CO)]ClO₄ (L = a tripodal tetraamine ligand = baep, abap, uns-penp, dppa, trpn) are reported. Geometric isomers are possible for all but the trpn complex, owing to the non-equivalence of the three arms on the tripodal ligand, and both NMR and X-ray crystallography are used to identify the single isomer formed. X-ray crystal structures of the complexes [(L)Co(O₂CO)]ClO₄ · xH₂O (L = baep, x = 0.5; L = abap, x = 0; L = uns-penp, x = 1; L = dppa, x = 0; L = trpn, x = 1) are reported; little variation is observed in the geometry of the carbonate chelate ring while significant lengthening of bonds and expansion of angles involving the cobalt ion occurs as the number of six-membered chelate rings in the complex cations increases. ⁵⁹Co NMR chemical shift data for the complexes show the expected linear relationship between λ_max, the wavelength of the lowest energy d–d transition, and γ, the magnetogyric ratio of the ⁵⁹Co nucleus. An excellent correlation between Δ, the d orbital splitting parameter, and δ(⁵⁹Co) also exists for these complexes. Rate data for the acid hydrolysis of [(L)Co(O₂CO)]⁺ (L = uns-penp, dppa) in 1.0 M HClO₄ differ by two orders of magnitude, and this is attributed to the differing steric accessibility of the endo O atoms in each complex. DFT calculations on the complexes reproduce the isomeric preferences, UV–Vis and ⁵⁹Co NMR spectroscopic data well, provided that solvent effects are included.     

Platinum(II) complexes of 8-quinolylmethylphosphonates: Synthesis,characterization and antitumour activity

A series of novel platinum(II) complexes of diethyl (8-dqmp) and monoethyl (8-Hmqmp) ester of 8-quinolylmethylphosphonic acid has been prepared and studied. It was shown that molecular or ionic complexes could be isolated by reaction of these organophosphorus ligands with [PtX₄]²⁻ (X = Cl, Br), depending on the acidity of the reaction solution. In the neutral medium diester formed dihalide adducts, trans-[Pt(8-dqmp)₂X₂] (1 and 2), with N-bonded ligand through the quinoline nitrogen. Under acidic conditions (pH < 3) both ligands gave the quinolinium salt complexes [LH]₂[PtX₄] (3 and 4, L = 8-dqmp; 7 and 8, L = 8-Hmqmp), with protonated quinoline ligand as cation and tetrahalidoplatinate complex as anion. By heating in methanol complexes 3 and 4 were converted into the corresponding dimeric hexahalidodiplatinum complexes, [8-Hdqmp]₂[Pt₂X₆] (5 and 6). The chelate complex [Pt(8-mqmp)₂] (9), with monoester ligand bonded through the quinoline nitrogen and the deprotonated phosphonic acid oxygen and forming two seven-membered {N, O} chelate rings, was obtained in neutral and basic media by reaction of platinum(II) halides either with sodium or hydrochloride salt of this monoester. The complexes were identified and characterized by elemental and thermogravimetric analyses, conductometric measurements, and by spectroscopic studies. In vitro antitumour activity of complexes was evaluated against the human epidermoid KB and murine leukaemia L1210 cell lines. These results were compared with those obtained for the palladium(II) complexes of the same phosphonate ligands and with those of platinum(II) and palladium(II) complexes of diethyl and monoethyl 2-quinolylmethylphosphonate, in order to correlate the structural and biological properties of quinoline-based aminophosphonate compounds.     

Nickel(II) derivatives of N-benzyliminodiacetate(2−) ligands,with and without imidazole: Synthesis,crystal structure and properties

In an attempt to prepare binary and ternary compounds, we have obtained two molecular complexes [Ni(MEBIDA or MOBIDA)(H₂O)₃]·nH₂O (n = 0 or 1) and two iso-type salts [Ni(Him)₆][Ni(MEBIDA or MOBIDA)₂]·4H₂O [MEBIDA = N-(p-methylbenzyl)iminodiacetate(2−) and MOBIDA = N-(p-methoxybenzyl)iminodiacetate(2−) ligands, Him = imidazole]. Our results are discussed with regard to related copper(II) and nickel(II) compounds. The reasons for which these chelating ligands produce nickel(II) salts instead of ternary compounds remain unclear since other iminodiacetate-like ligands give true ternary Ni(II) compounds with imidazole and other N-heterocyclic ligands.     

Metal coordination architectures of N-acyl-salicylhydrazides: The effect of metal ions and steric repulsion of ligands to their structures of polynuclear metal complexes

Three polynuclear transition metal complexes [Mn₈(DMF)₈(L1)₈] · 4DMF (1), [Mn₆(DMF)₆(L2)₆] · [Mn₆(DMF)₄(H₂O)₂(L2)₆] · 2DMF (2), [Cu₃(L3)₂(py)₂] (3) of the pentadentate ligands N-acyl-salicylhydrazides were synthesized and characterized, their crystal structures were investigated. The oxidation state and properties of the central metal ions are important in crystal structure formation, trivalent Mn(III) ion which easily form stable octahedral coordination metallamacrocycle complexes, metallacrowns 1 and 2 were obtained; while bivalent Cu(II) ion is easier to form square planar, trinuclear complexes 3 was obtained. The steric effect of the N-acyl side chains also plays an important role in the structures of these polynuclear complexes. The magnetic property of 1 was also investigated.     

Bridged bis(amidinate) lanthanide complexes: Synthesis,molecular structure and reactivity

The yttrium chloride with the bridged bis(amidinate) L (L = Me₃SiNC(Ph)N(CH₂)₃NC(Ph)NSiMe₃) LYCl(DME) (2) was synthesized and structurally characterized. Treatment of LLnCl(sol)_x (Ln = Yb, sol = THF, x = 2 1; Ln = Y, sol = DME, x = 1 2) with the dilithium salt Li₂L(THF)_0.5 afforded the novel bimetallic lanthanide complexes supported by three ligands, Ln₂(μ₂-L)₃ · DME (Ln = Yb 3, Y 4; DME = dimethylether), instead of the designed complex LLn(μ₂-L)LnL via the ligand redistribution reaction. Complexes 3 and 4 were fully characterized including X-ray analysis and ¹H NMR spectrum for 4. Reaction of LnCl₃ (Ln = Yb, Y) with 2 equiv. of Li₂L(THF)_0.5 gave the anionic complexes [Li(DME)₃][L₂Ln] (Ln = Yb 5, Y 6), which were confirmed by a crystal structure determination. The further study indicated that complexes 3 and 4 can also be synthesized by reaction of LnCl₃ (Ln = Yb, Y) with 1.5 equiv. of Li₂L(THF)_0.5 or reaction of 1 and 2 with anionic complexes 5 and 6. Complexes 3, 4, 5 and 6 were found to be high active catalysts for ring-opening polymerization of ε-caprolactone (CL).     

Neutral and cationic cyclometallated Ir(III) complexes of anthra[1,2-d]imidazole-6,11-dione-derived ligands: Syntheses, structures and spectroscopic characterisation

The syntheses of two new ligands and five new heteroleptic cyclometallated Ir(III) complexes are reported. The ligands are based upon a functionalised anthra[1,2-d]imidazole-6,11-dione core giving LH¹⁻³ incorporating a pendant pyridine, quinoline or thiophene unit respectively. Neutrally charged, octahedral complexes [Ir(ppy)₂(L¹⁻³)] are chelated by two cyclometallated phenylpyridine (ppy) ligands and a third, ancillary deprotonated ligand L¹⁻³, whilst cationic analogues could only be isolated for [Ir(ppy)₂(LH¹⁻²)][PF₆]. X-ray crystal structures for [Ir(ppy)₂(L¹)], [Ir(ppy)₂(LH¹)][PF₆] and [Ir(ppy)₂(L²)] showed the complexes adopt a distorted octahedral coordination geometry, with the anthra[1,2-d]imidazole-6,11-dione ligands coordinating in a bidentate fashion. Preliminary DFT calculations revealed that for the complexes of LH¹ and LH² the LUMO is exclusively localized on the ancillary ligand, whereas the nature of the HOMO depends on the protonation state of the ancillary ligand, often being composed of both Ir(III) and phenylpyridine character. UV-vis. and luminescence data showed that the ligands absorb into the visible region ca. 400 nm and emit ca. 560 nm, both of which are attributed to an intra-ligand CT transition within the anthra[1,2-d]imidazole-6,11-dione core. The complexes display absorption bands attributed to overlapping ligand-centred and ¹MLCT-type electronic transitions, whilst only [Ir(ppy)₂(L²)] appeared to possess typical ³MLCT behaviour (λ_em = 616 nm; τ = 96 ns in aerated MeCN). The remaining complexes were generally visibly emissive (λ_em ≈ 560-570 nm; τ < 10 ns in aerated MeCN) with very oxygen-sensitive lifetimes more indicative of ligand-centred processes.     

Star-shaped electrochemiluminescent metallodendrimers with central polypyridyl Ru(II) complexes: Synthesis and their photophysical and electrochemical properties

Several dendritic bridging ligands were designed and synthesized to develop more sensitive and efficient electrochemiluminescent (ECL) polynuclear Ru(II) complexes. Various types of novel two-armed, four-armed and six-armed tris(bipyridyl)ruthenium core dendrimers were synthesized by coordinating dendritic polybipyridyl ligands with Ru(II) complexes, and the effect of the ligand and the dendritic network on the ECL characteristics were studied. Their electrochemical redox potentials, UV, photoluminescence (PL), and relative ECL intensities were also investigated in detail. The synthesized metallodendrimers exhibited strong metal-to-ligand charge transfer (MLCT) absorption at 428-451 nm and emission at 591-601 nm. Most of the newly synthesized metallodendrimers showed enhanced ECL intensities compared to the reference complex, [Ru(o-phen)₃](PF₆)₂. In particular, the ECL intensities of the six-armed heptanuclear ruthenium complexes were almost four times greater than that of [Ru(o-phen)₃]²⁺. These metallodendrimers could be utilized as efficient ECL materials and light emitting devices.     

Synthesis,structures and mass spectrometry of lanthanide nitrate complexes with tricyclohexylphosphine oxide

The complexes Ln(NO₃)₃(OPCy₃)₃(EtOH)_x (Cy = cyclohexyl, C₆H₁₁x = 0 for Ln = Eu, Er, x = 0.5 for Ln = La, Nd and x = 1 for Ln = Tm, Yb) have been prepared by reaction of lanthanide nitrates with Cy₃PO in ethanol. The single crystal X-ray structures for Ln = La, Nd, Eu, Er, Tm and Yb are reported. The structures for Ln = La–Eu have two molecules in the unit cell in which the nitrates are all bound as bidentate ligands. The unit cell for Ln = Er contains two distinct molecules; one with three bidentate nitrates and one with two bidentate and one monodentate nitrate. The Tm and Yb complexes have one molecule in the unit cell with two bidentate and one monodentate nitrate ligands. The monodentate nitrates are hydrogen bonded to ethanol in the Tm and Yb structures but not in the Er complex. The infrared spectra of the three classes of complex do not readily permit identification of the monodentate nitrate groups. Electrospray mass spectrometry indicates that redistribution/ionisation reactions occur in solution. Ions formed by solvolysis reactions are attributed to gas phase processes associated with the electrospray technique. Tandem mass spectrometry for the La, Ho and Yb complexes shows that in the gas phase loss of Cy₃PO is the sole fragmentation pathway for all but the Yb complex where the higher energy required for initial fragmentation leads to a more complex fragmentation pattern.     

The synthesis,characterization and melting properties of thiophene-containing dithiocarboxylate complexes of nickel(II)

The reactions of a series of 5-alkyl-2-thiophenedithiocarboxylates with nickel(II) chloride afforded two types of complexes, blue nickel(II) complexes with two terminal dithiocarboxylate ligands, [Ni(S₂CTR)₂] and violet nickel(II) complexes with perthio- and dithiocarboxylate ligands, [Ni(S₂CTR)(S₃CTR)] (where T = 2,5-disubstituted thiophene, R = C_nH_2n+1, n = 4, 6, 8, 12, 16). The blue monomers are preferred for the shorter chains (C₄ and C₆) and the violet compounds form exclusively for the longer chains (C₈, C₁₂, and C₁₆) in the alkylthiophene complexes. In addition to the above series, [Ni(S₂CTCH₃)₂], was prepared in a one-pot reaction in THF and both the blue and violet products were isolated. It was possible to convert the blue complexes [Ni(S₂CTR)₂] (R = butyl, hexyl) into the corresponding violet complexes [Ni(S₂CTR)(S₃CTR)] after stirring in THF solutions for prolonged periods of time. Liquid-crystalline properties of these complexes were examined by DSC and POM. The violet complexes with C₈ and C₁₂ alkyl chains showed liquid-crystalline properties.     

Redox-active antifungal cobalt(II) and copper(II) complexes with sterically hindered o-aminophenol derivatives

Co(II) complexes with 4,6-di(tert-butyl)-2-aminophenol (HL^I) and 2-anilino-4,6-di(tert-butyl)phenol (HL^II) have been synthesized and characterized by means of physico-chemical methods. The compounds HL^I and HL^II coordinate in their singly deprotonated forms and behave as bidentate O,N-coordinated ligands; their low-spin Co(II) complexes are characterized by CoN₂O₂ coordination modes and square planar geometry. Both the free ligands and their Co(II) and Cu(II) complexes (we have produced and characterized the latter before) exhibit a pronounced antifungal activity against Aspergillus niger, Fusarium spp., Mucor spp., Penicillium lividum, Botrytis cinerea, Alternaria alternata, Sclerotinia sclerotiorum, Monilia spp., which in a number of cases is comparable with that of Nystatin and Terbinafine or even higher. The reducing properties of the ligands and their metal(II) complexes, as well as their antifungal activities, were found to decrease in the order: Cu(L^I)₂ > Cu(L^II)₂ ? Co(L^I)₂ > Co(L^II)₂ > HL^I > HL^II.