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Mixed-ligand polymeric and binuclear silver(I) complexes with azaheterocyclic ligands and the closo-decaborate anion of the composition [Ag2L[B10H10]]n and [Ag2L2[B10H10]] (L = bipy, bpa, and phen) are synthesized and studied by IR-spectroscopy and X-ray powder diffraction. The complexes are prepared by the reaction between [Ag2[B10H10]] and ligand L in organic solvents. It is found that polymeric and binuclear complexes are selectively formed depending on the solvent used. When the reaction proceeds in acetonitrile, polymeric complexes are isolated. When DMF is used, binuclear complexes are formed which explains by the complete dissociation of the starting [Ag2[B10H10]] complex. The structures of [Ag2(bipy)[B10H10]]n and [Ag2(bpa)2[B10H10]]·DMF are determined by X-ray diffraction.

The present work describes the results of treatment of two pentacoordinated copper(II) complexes with 1,10-Phenanthroline (PHEN). During the course of the reaction, in situ generated PHEN-Cu complex has mediated the ligand transformations. In spite of the structural similarities of the precursor complexes used, structurally distinct unusual mixed ligand complexes viz. dichlorido (3-methyl [1,2,4] triazolo[3,4-b] [1,3] benzothiazole) 1,10-phenanthroline copper(II) and dichlorido-µ-N,N-benzimidazolato dibenzimidazole di-1,10-phenanthroline dicopper (II) chloride are formed. These complexes are characterized by IR, ESI-MS, EPR and UV–Vis spectral studies. X-ray crystal structures of both the complexes are described. Further, the observed results have inspired the synthesis of 3-methyl [1,2,4] triazolo[3,4-b] [1,3] benzothiazole, by a new synthetic approach.

The new mixed ligand copper(II) complexes [Cu(HL)(H2O)(A)]·2H2O (1, NaH2L = sodium (Z)-2-(2-(1,3-dioxo-1-(phenylamino)butan-2-ylidene)hydrazinyl)benzenesulfonate, A = dimethylsulfoxide, [Cu(HL)(H2O)(B)] (2, B = 1,3,4-thiadiazol-2-amine), [Cu(HL)(H2O)(Y)]·1/2CH3OH (3, C = hexamethylenetetramine) and [Cu(HR)2(H2O)2](H2L)2 (4, HR = methyl picolinimidate derived from 2-cyanopyridine) were synthesized and characterized by IR and ESI-MS spectroscopies, elemental and X-ray crystal structural analyses. These compounds act as homogenous catalysts for the cyanosilylation reaction of a variety of both aromatic and aliphatic aldehydes with trimethylsilyl cyanide affording the corresponding cyanohydrin trimethylsilyl ethers in high yields (up to 85–99 %) in methanol and at room temperature.

Four isostructural 3D lanthanide metal-organic frameworks (Ln-MOFs) {[Ln(L)(ox)0.5(H2O)2]·H2O}n (Ln = Pr 1, Nd 2, Sm 3 and Eu 4) were constructed by 5-hydroxyisophthalic acid (H2L) and oxalate (ox) through solvothermal methods, which show a (4,5)-connected tcs net with the point symbol of (44·62)(44·66). Compound 4 exhibits an intense red fluorescence in solid state and is an excellent dual-functional recyclable luminescent sensor which can sense acetone and Cu2+ with high sensitivity and selectivity simultaneously.

A copper(II) complex of (R)-N-(2-pyridylmethyl)pipecolate (pmpi) was prepared, and its structure was revealed by X-ray crystal structure analysis. Mixed ligand complexes were then prepared from this complex and (R)- and (S)-N-(t-butoxycarbonyl)leucinate (BocLeu). The (R)-BocLeu complex is less soluble in aqueous acetonitrile and more soluble in acetone than the (S)-BocLeu complex, and the reason was discussed on the basis of their structures. Recrystallization of the reaction mixture consisting of Cu(II) ion, pmpi, and (RS)-BocLeu from aqueous acetonitrile gave the (R)-BocLeu complex and that from acetone gave the (S)-BocLeu complex.

The mixed-ligand coordination polymers {[Zn(BIX) 2.5 ](NO 3 ) 2 ·5.5H 2 O} n ( 1 ), {[Co(BIX)(HBTC)](BIX) 0.5 ·H 2 O} n ( 4 ), [Ni(BIX) 2 (BDC)(H 2 O)] n ( 5 ), [Zn(BIX)(PDC)] n ( 6 ), [Ni(BIX)(PDC)(H 2 O)] n ( 7 ) and [Zn(BIX) 0.5 (HIDC)] n ( 8 ) were synthesized, structurally characterized and compared to the known coordination polymers {[Co(BIX) 3 ](NO 3 ) 2 ·4H 2 O} n ( 2 ) and {[Zn 2 (BIX)(BTC)(OH)]·H 2 O} n ( 3 ) to determine the mutual influence of an anionic carboxyl ligand and a neutral N-donor ligand (BIX = 1,4-bis((1H-imidazol-1-yl)methyl)-benzene; H 3 BTC = 1,2,3-benzene-tricarboxylic acid; H 2 BDC = 1,3-benzene-dicarboxylic acid (isophthalic acid); H 2 PDC = 3,4-pyridine-dicarboxylic acid; H 3 IDC = 4,5-imidazole-dicarboxylic acid). Compound 1 is a 1D ladder-like structure with two bridging and one terminal (dangling) BIX ligand. Neighboring ladders mutually entangle with the dangling BIX ligand being threaded through {Zn 4 (BIX) 4 } openings from adjacent strands. Compound 2 shows a 3D pcu -network with octahedrally coordinated cobalt ions bridged by three crystallographically different inversion-symmetric BIX ligands. The overall structure motifs in the mixed-ligand compounds are 1D metal-carboxylate chain-structures, bridged by neutral BIX ligands to form either 1D ladder-like strands ( 4 ), 2D networks ( 3 , 5 with square lattice, 4,4 or sql topology, 7 , 8 with honeycomb, 6,3 or hcb topology) or 3D frameworks ( 6 with diamond, 6,6 or dia topology). Noteworthy, compound 4 forms a 1D tubular structure of stacked {Co 2 (BIX) 2 } metallacycles that are threaded with uncoordinated BIX ligands like a rotaxane. A tetrahedral asymmetric Zn atom is formed in the crystals of 6 with spontaneous resolution as only one Zn configuration assembles into the 3D chiral framework of each single crystal.

Energy-transfer rate-constants, k1, from photo-excited mixed-ligand [Ru(phen)3−n(4dmb)n]2+ (n = 0–3; phen = 1,10-phenanthroline, 4dmb = 4,4′-dimethyl-2,2′-bipyridine) to [Cr(O–O)3]3− (O–O2− = ox2− ((COO−)2), mal2− (CH2(COO−)2)) and [Cr(CN)6]3− in encounter complexes were evaluated in aqueous solutions. The dependence of the evaluated k1 values on the number of 4dmb, n, is divided into the following three types; the k1 values (i) are independent of n in [Cr(CN)6]3− system, (ii) decrease gradually as n increases in [Cr(ox)3]3− system, and (iii) drop suddenly from n = 0 to n = 1 in [Cr(mal)3]3− system. These results indicate that [Cr(ox)3]3− would exist equivalently around [Ru(phen)3−n(4dmb)n]2+ in encounter-complex in [Ru(phen)3−n(4dmb)n]2+–[Cr(ox)3]3− system. However, in [Ru(phen)3−n(4dmb)n]2+–[Cr(mal)3]3− system, [Cr(mal)3]3− would exist selectively near ligand-4dmb of [Ru(phen)2(4dmb)]2+ in aqueous solution (anisotropic). Ligand congeniality between ligand-4dmb of [Ru(phen)3−n(4dmb)n]2+ and ligand-mal of [Cr(mal)3]3− would be better than that between ligand-phen and ligand-mal in the encounter complex. [Cr(CN)6]3− could penetrate between the ligand-phen and/or ligand-4dmb in [Ru(phen)3−n(4dmb)n]2+ without being interrupted by methyl-base of ligand-4dmb because the k1 values in [Ru(phen)3−n(4dmb)n]2+–[Cr(CN)6]3− system are very large and almost constant. In addition, we correct the mistake of the kq and k1 value of [Ru(phen)3]2+–[Cr(mal)3]3− in LiCl aqueous solution in our previous paper.

1,1-Bis[5-(pyridine-2-yl)-1,2,4-triazol-3-yl]methane have been used to prepare ternary lanthanide complexes in which the remaining ligands are different diketonate-anions. The complexes were characterized by various measurements including single-crystal X-ray crystallography. The characteristic photophysical properties of these complexes, i.e. the absorption and luminescence spectra, the metal-centred lifetimes and the overall luminescence yields were measured. All title complexes show strong sharp red emissions in the solid state, corresponding to 5D0 → 7FJ (J = 0–3) transitions with 5D0 → 7F2 (612–621 nm) as the most prominent one. Three-layer light-emitting diodes based on PVK doped with the title complexes as active layer were fabricated and examined.

pH-potentiometry, calorimetry and 1Н and 13С NMR spectroscopy have been used to study the mixed-ligand complex formation in the systems Hg2+–Edta4−–L− (L = GlyGly, AlaAla) in aqueous solution at 298.15 K and ionic strength of I = 0.5 (KNO3). The thermodynamic parameters of formation of the HgEdtaL3−, and HgEdtaLH - 1 4 - complexes have been determined. The most probable coordination mode for the complexone and the dipeptide in the mixed-ligand complexes was discussed.

Four pentacoordinated square-pyramidal Cu(II) complexes with the general formula [Cu(L)(X)], where L is a l -histidine derived tetradentate ligand and X is either 3-hydroxypyridine or 2-methylpyridine, has been synthesized. Structural analysis showed that the presence of water filled one dimensional chiral channel in the lattices. The interiors of the channels were varied using aromatic ring substitution on the ligand as well as on the monodentate ligand. The dimensions of the channels range from ∼7 to 9 A.

The synthesis and characterization of the neutral 2+1 mixed ligand complex fac- Re(CO) 3 (acac)(isc) ( 4 ) with acetylacetonate (acac) as the bidentate ligand and an isocyanide (the isocyanocyclohexane, isc) as the monodentate ligand is described. The synthesis of 4 proceeds through the intermediate formation of the fac- Re(acac)(H 2 O)(CO) 3 precursor complex 2 . Complex 4 was characterized by elemental analysis, spectroscopic methods, and X-ray crystallography showing a distorted octahedral arrangement of the ligands around Re. At technetium-99m level, the corresponding fac - 99m Tc(acac)(isc)(CO) 3 complex 5 was obtained in high yield by reacting the fac - 99m Tc(acac)(H 2 O)(CO) 3 precursor complex 3 with isocyanocyclohexane and its structure was established by chromatographic comparison with the prototypic rhenium complex using high performance liquid chromatography.

Two hitherto unknown mixed-ligand tris chelated complexes containing 2-aminothiophenolate, [Et4N]2[MIV(NH–(C6H4)–S)(mnt)2] (M = Mo, 1a; W, 2a) and two mixed-ligand tris chelate complex containing N,N-diethyldithiocarbamate, [Et4N]2[MIV(Et2NS2)(mnt)2] (M = Mo, 1b; W, 2b) have been synthesized and characterized structurally. Although these complexes are supposed to be quite similar to the well-known symmetric tris chelate complexes of maleonitriledithiolate (mnt), [Et4N]2[MIV(mnt)3] (M = Mo, 1c; W, 2c), but display both trigonal prismatic and distorted trigonal prismatic geometry in their crystal structure indicating the possibility of an equilibrium between these two structural possibilities in solution. Unlike extreme stability of 1b, 2b, 1c and 2c, both 1a and 2a are highly unstable in solution. In contrast to one reversible reduction in case of 1b and 2b, 1a and 2a exhibited no possible reduction up to −1.2 V and two sequential oxidation steps which have been further investigated with EPR study. Differences in stability and electrochemical behavior of 1a, 1b, 2a and 2b have been correlated with theoretical calculations at DFT level in comparison with long known 1c and 2c.

Strategically designed and synthesized three isomorphous mononuclear complex, M(bpee)2(6-me-2,3-pyrdcH)2 [M = CoII (1), NiII (2) and FeII (3)] using the mixed ligand system. Structure determination reveals that each mononuclear fragment is engaged in bidirectional H-bonding (O–H···N) interactions forming a 2D supramolecular rectangular grid. Each rectangular grid undergoes threefold interpenetration resulting a 2D interpenetrated supramolecular framework with hydrophobic small pores. CO2 sorption at 195 K in 1 shows no occlusion in the pore surface, however hysteretic sorption observed with H2O and MeOH, correlated with the H-bonding interaction of H2O and MeOH with the pendant carboxylate O-atoms, which are aligned on the 2D surface.

The structure of {HC(3,5-Me2pz)3Fe[μ-p-C6H4(CH2OCH2C(pz)3)2]Fe(3,5-Me2pz)3CH}(BF4)4 (pz = pyrazolyl ring) contains two octahedral iron(II) centers linked by a semirigid, bitopic tris(pyrazolyl)methane ligand. The solid-state structure shows the two heteroleptic-bonded iron(II) centers are low-spin at 200 K and situated in a trans orientation with respect to the central linking arene ring.

Oxorhenium(V) complexes with ‘3+1’ mixed ligands, [ReO(SSS)L], where SSS is η 3 -(SCH 2 CH 2 SCH 2 CH 2 S), L = η 1 -(C 6 H 4 COOH-4-S), η 1 -(C 6 H 4 CONHCH 2 COOEt-4-S), η 1 -(C 6 H 4 CONHCH(CH 3 )COOEt-4-S), and η 1 -(C 6 H 4 CONHCH(CH 2 Ph)COOEt-4-S), have been synthesized. These L ligands and [ReO(SSS)L] complexes were characterized by IR, 1 H NMR, 13 C NMR, and MAS spectrometers. Molecular structure of [ReO(SSS){η 1 -(C 6 H 4 COOH-4-S)}] complex was determined to be a distorted square pyramidal by single crystal X-ray analytical method.

New mixed polypyridyl {NMIP = 2′-(2″-nitro-3″,4″-methylenedioxyphenyl)imidazo-[4′,5′-f][1,10]-phenanthroline, dmb = 4,4′-dimethyl-2,2′-bipyridine, bpy = 2,2′-bipyridine} ruthenium(II) complexes [Ru(dmb)2(NMIP)]2+ (1) and [Ru(bpy)2(NMIP)]2+ (2) have been synthesized and characterized. The binding of these complexes to calf thymus DNA (CT-DNA) has been investigated with spectroscopic methods, viscosity and electrophoresis measurements. The experimental results indicate that both complexes could bind to DNA via partial intercalation from the minor/major groove. In addition, both complexes have been found to promote the single-stranded cleavage of plasmid pBR 322 DNA upon irradiation. Under comparable experimental conditions compared with [Ru(phen)2(NMIP)]2+, during the course of the dialysis at intervals of time, the CD signals of both complexes started from none, increased to the maximum magnitude, then no longer changed, and the activity of effective DNA cleavage dependence upon concentration degree lies in the following order: [Ru(phen)2NMIP]2+ > complex 2 > complex 1.

Reactions of Sr(II) and Ba(II) chlorides with 2-hydroxybenzophenone and salicylaldehyde, hydroxyaromatic ketones or β-diketones in 1:1:1 molar ratios have resulted in the formation of mixed ligand complexes of the type [MLL′(H2O)2] (M = Sr(II) or Ba(II); HL = 2-hydroxybenzophenone and HL′ = salicylaldehyde, 2-hydroxyacetophenone, 2-hydroxypropiophenone, pentane-2,4-dione, 1-phenylbutane-1,3-dione or 1,3-diphenylpropane-1,3-dione). These complexes have been characterized by elemental analyses, TLC, IR and 1H NMR spectroscopy.

The mixed ligand complexes [{Gd(OCMe2-i-Pr)2Cp}2], [{Sm(OCMe2-i-Pr)2Cp}2], and [Sm2(OCMe2-i-Pr)3Cp3] were synthesized by reacting [LnCp3] with HOCMe2-i-Pr. X-ray crystallographic studies show that the three complexes each have two bridging alkoxide ligands linking two metal atoms. The coordination geometries at the metals are distorted tetrahedral.

The Au(I)-SO32- - S2O32- system was studied at 25°C and at I = 0.1 M NaClO4 using hydrodynamic voltammetry, gold potentiometry, UV-Vis spectrophotometry and Raman spectroscopy. The presence of two mixed-ligand species, Au(S 2O3)(SO3)3- and Au(S 2O3)(SO3)25-, was detected from the Raman experiments and supported by the gold potentiometric experiments. The stepwise formation constant, log K11r, for the reaction Au(S 2O3)23-+rSO32-⇔Au(S2O3)(SO3)r-(2r+1)+S2O32- was found to be 1.1 (r = 1) and 4.8 (r = 2) from the hydrodynamic voltammetric experiments.

Complexes of the type (R-bpy)2RuCl2 (R: H, Me, tert-but) were synthesised by microwave-activated reactions of [Ru(cod)Cl2]n with substituted 2,2′-bipyridines in dimethylformamide as the solvent. The complexes were isolated in high yields and high purity from the reaction mixture. Microwave-assisted or thermal reaction of the (R-bpy)2RuCl2 solutions with substituted bibenzimidazoles, 1,10 phenanthroline or bipyrimidine in dmf/water mixtures resulted in the formation of mixed ligand complexes of the type [(R-bpy)2Ru(L–L)]Cl2. The complexes were characterised by NMR spectroscopy and MS. Furthermore, their photochemical and electrochemical properties were investigated and the solid state structure of (4-tert-butyl-bpy)2RuCl2 (3), [(4-tert-butyl-bpy)2Ru(tetramethylbibenzimidazole)](PF6)2 (4), and [(4-tert-butyl-bpy)2Ru(bipyrimidine] (PF6)2 (5) was determined by X-ray diffraction analysis of single crystals.

Two new mixed ligand complexes of copper(II) with N , N , N ′ , N ″, N ″-pentamethyldiethylenetriamine and polypyridine ligands have been prepared and characterized by means of spectroscopic, magnetic and single-crystal X-ray diffraction methods. These two complexes are isomorph and isostructure in which the coordination polyhedron about the copper(II) ion is distorted square pyramidal. [Cu(PMDT)(bipy)] 2+ and [Cu(PMDT)(phen)] 2+ show an absorption wavelength maximum at 625 and 678 nm, respectively, assigned to the d–d transition. Antibacterial, antifungal and superoxide dismutase activities of these complexes have also been measured. It was observed that [Cu(PMDT)(bipy)](ClO 4 ) 2 was more effective against P. Pyocyanea and Klebsiella sp. than S. aureus. Similarly, Fusarium sp. was highly susceptible against [Cu(PMDT)(bipy)](ClO 4 ) 2 but less susceptible against [Cu(PMDT)(phen)](ClO 4 ) 2 .

Chemical speciation from computer simulation of complexing permits blends of two or more ligands to target pivotal metal roles in industrial processes and to optimise ligand use and efficiency. Examples are given of employing sequestering agents in the pulp industry and in the foliar feeding of growing agricultural crops. Ligand efficiency savings of tenfold or more are achievable and savings of experimental time as large as one 100-fold are possible at the research lab and pilot stages of a project. Bespoke blends of ligands can be speciation designed to specifically match an industrial/raw materials scenario.

The synthesis of mixed ligand [Ru(NH3)3(dpop′)]2+ and [Ru(tpy)(dpop′)]2+ (dpop′=dipyrido(2,3-a:3′,2′-j)phenazine; tpy=2,2′:6′,2″-terpyridine) complexes is described. Absorption, emission, electrochemistry and stability of the series of [Ru(L)1,3(dpop′)]2+ (L=dpop′, tpy and NH3) complexes is evaluated. Absorption spectra show the Ru(dπ)→dpop′(π*) CT transition energies increase when the ancillary ligands are varied in the order NH3, tpy and dpop′, consistent with increased Ru2+/3+ oxidation potentials in the same order. The [Ru(tpy)(dpop′)]2+ ion is emissive in room temperature de-oxygenated CH3CN with λem=748 nm. At 77 K, the [Ru(tpy)(dpop′)]2+ ion displays emissions at λem=600; 645(sh) and λem=735 nm attributed to [Ru(tpy*)(dpop′)]2+ and [Ru(tpy)(dpop′*)]2+3CT excited state relaxations. Spectro-electrochemistry shows the bis-tridentate [Ru(tpy)(dpop′)]2+ complex is reversible upon oxidation and reduction, while [Ru(NH3)3(dpop′)]2+ is irreversible.

Subvalent mercury clusters [Hg 3 (LL) 3 ] 4+ with LL=dpam (dpam=Ph 2 AsCH 2 AsPh 2 ) or Ph 2 AsCH 2 PPh 2 and dpam–dppm (dppm=Ph 2 PCH 2 PPh 2 ) or dpam–Ph 2 AsCH 2 PPh 2 mixed ligand complexes were obtained by reaction of [Hg 2 ] 2+ with the ligands or by reduction of a mixture of [Hg(Me 2 SO) 6 ](O 3 SCF 3 ) 2 and the ligands with elemental mercury. Whereas the equilibrium 2Hg 2+ +Hg⇌[Hg 3 ] 4+ is far to the right in the presence of the ligands dpam or dppm, only ca. 20% conversion is observed for Ph 2 AsCH 2 PPh 2 . The clusters are characterized by FAB MS and multinuclear NMR spectroscopy. The 199 Hg– 199 Hg coupling constants of [Hg 3 (μ-dpam) 2 (μ-dppm)](O 3 SCF 3 ) 4 have values of 17 800 and 23 600 Hz. The fragmentation of [Hg 3 (μ-dpam) 3 ](O 3 SCH 3 ) 4 gives [Hg 2 (μ-dpam) 2 ](O 3 SCH 3 ) 4 which is characterized by single-crystal X-ray diffraction.

Mixed-ligand Fe(II)-1,10-phenanthroline complexes containing zero, one, two, or three ligands with triethoxysilyl termini were incorporated into Ce(IV)-containing silica sol–gels by doping the sols prior to gelation. The alkoxysilyl termini ensured that the complexes were covalently bound to the silica gels. Complexes attached to the gels were significantly more stable towards oxidation by Ce(IV) than complexes bearing no tethers. The mixed ligand complexes can be prepared only as a mixture of species due to the unusual trend for binding constants between phenanthroline and iron (H. Irving, D.H. Mellor, J. Chem. Soc. (1962) 5222). Statistical analysis of the data for the mixtures revealed a sigmoid dependence of the stabilization with respect to the number of tethers. Contributions from inner-sphere pathways are believed to account for this non-monotonic dependence.

In order to assess the solution state of VO(IV) in organisms when administered in the form of the bis(maltolato) complex (VO(malt) 2 ), ternary systems of VO(IV)—maltol with various bioligands (potential metal ion binders of biofluids and tissues), such as inorganic phosphates, adenosine nucleotides, catechol derivatives, citrate and oxalate, were studied. The speciation of VO(IV) in these ternary systems was studied by pH-potentiometry, while the binding modes of the complexes were determined by spectral (UV—Vis and electron paramagnetic resonance) methods. The results support strongly the assumption that VO(malt) 2 undergoes transformation into mixed ligand complexes formed with the various VO(IV) binders of biological fluids and tissues.

Interaction of the complex [ReO((C 2 H 5 ) 2 NCH 2 CH 2 N(CH 2 CH 2 S) 2 )(4-CH 3 OC 6 H 4 S)] ( 1 ) with glutathione (GSH) in DMSO- d 6 led to isolation of the complex [ReO((C 2 H 5 ) 2 NCH 2 CH 2 N(CH 2 CH 2 S) 2 )(GS)] ( 2 ) in which glutathione has replaced the coligand 4-methoxy-thiophenol. Identification of 2 was achieved by MS, NMR, UV-Vis, and IR spectroscopies. The interaction of glutathione with the complex [ 99m TcO((C 2 H 5 ) 2 NCH 2 CH 2 N(CH 2 CH 2 S) 2 )(4-CH 2 OC 6 H 4 S)] ( 3 ), which is analogous to 1 , was also studied at tracer level by HPLC and it was demonstrated that the complex [ 99m TcO((C 2 H 5 ) 2 NCH 2 CH 2 N(CH 2 CH 2 S) 2 )(GS)] is also formed. Complex 3 is a representative of the [ 99m TcO(SNS)(S)] class of potential brain imaging agents that show high brain uptake and retention in animals tested. The replacement of the coligand 4-methoxythiophenol by glutathione transforms the originally lipophilic complex to hydrophilic; this is being investigated further as one of the possible pathways in the retention mechanism of this type of complex.

Stabilities of the mixed-ligand copper (II) complexes [Cu (pmdt) (Am)] + containing N , N , N ′, N ″, N ″-pentamethyldiethylenetriamine (pmdt) and 10 different α-amino acid anions (Am − ) and their absorption, CD and ESR spectra are reported. The effect of the C- and N-substituent groups of the amino acid ligand on stability is examined. It was found that the stability depression of the N-substituent is large, while that of the C-substituent is quite small without regard to its bulkiness. The d-d absorption and X- and Q-band ESR spectra suggest that the ternary complexes are of the five-coordinate type with a trigonal bipyramid-based geometry, which causes the distinguishable substituent effect.

The title compounds were optically investigated by recording the 10 K absorption spectra of the Cs and n-tetrabutylammonium salts pressed in KBr pellets and the 10–20 K emission spectra of the complex ions doped into Cs 2 SnCl 6 . For d-d transitions the spectral region is limited to the range from about 4000–12000 cm −1 . The measured peaks are assigned to zero-phenon transitions (electronic origins) between states belonging to the (t 2g ) 4 subshell configuration and to corresponding vibronic transitions. For the better resolved spectra an assignment to symmetries of respective point groups can be obtained from selection rules using relative peak intensities. These results must be, however, considered as still tentative.

Reactions of (Bu4N)TcNX4 (X = Cl, Br) and (Bu4N)TcOCl4 with sodium azide in acetonic solutions are studied by EPR. During the reactions mixed-ligand complexes of the type [TCNXn(N3)4−n]− (n=0–4) are formed which can be characterized by their EPR spectral data. The parameters of the individual species strongly depend on the composition of the equatorial coordination sphere. [TcN(N3)4]− is characterized by a nearly isotropic frozen solution EPR spectrum (g∥=1.979; g⊥=1.982). By means of an MO model the covalency of the Tc(equatorial)-ligand bond was found to be higher than those in analogous halide complexes.

A NDDO method capable of calculating configuration interaction for transition-metal compounds is applied to mixed ligand complexes [Co(NH 3 ) 5 L] n+ (L=Cl − , OH − , H 2 O, CN − , NH 3 ). The parameters used are discussed. The calculated transition energies are in fairly good agreement with experimental data.

In the complex HTc(N 2 )(dppe) 2 the nitrogen ligand is most labile and can be exchanged under mild conditions for CO, isonitriles and phosphites (L 1 ), yielding neutral hydridocomplexes of Tc(1) HTcL 1 (dppe) 2 . HTc(CO)(dppe) 2 is also formed from the title compound by CO abstraction from methanol. In the complexes HTcL 1 (dppe) 2 the hydrido ligand can be exchanged for acetonitrile (L 2 ), yielding cationic mixed-ligand complexes of Tc(I) TcL 1 L 2 (dppe) 2 + , which are isolated as hexafluorophosphates.

Ru(II) and Ru(III) complexes of the biologically active tridentate NNS donors 2-formylpyridine(4- phenyl) thiosemicarbazone (L1H) and 2-formylpyridine thiosemicarbazone (LH) have been synthesized and characterized by elemental analysis, conductance and magnetic susceptibility measurements, as well as by spectroscopic techniques such as UV—Vis, IR and NMR. A series of mononuclear bis chelates of the formulae [Ru(L1H)2](SCN)2, [Ru(L1H)(L1)] Cl, [Ru(L1)2], [Ru(L)(LH)]ClO4·2H2O and mononuclear mixed ligand complexes such as [Ru(L1H)Cl2(CH3OH)], [Ru(L1H)(imz)Cl2], [Ru(L1H)(2-pico)(imz)]ClO4, [Ru(L1H)(TTSC)]Cl·12(C2H5)2O, [Ru(L1H)(imz)(thiosal)]Cl·CH3OH, [Ru(L1H)(bipy)Cl]Cl2·CH2Cl2 have been isolated and characterized. Binuclear complexes [Ru2(L1)2(OH)2], [Ru2(L1)2Cl4]·4H2O, [Ru2(L1)2(SCN)4]·H2O, [Ru2(L1)(imz)Cl4]·3CH3OH, [Ru2(L1)(H2O)Cl4] have also been synthesized and characterized. From the analysis of spectroscopic and magnetic data the donor sites of the ligands have been located and the geometries of the donor environment around the Ru(II)/Ru(III) acceptor centre have been proposed.

A novel, water soluble, electrically neutral polynuclear iron(III) mixed ligand complex has been prepared for use in parenteral iron therapy. The composition of the new compound has been determined by preparative and analytical methods. Osmomotic pressure measurements have shown its polymeric nature. The complex molecule has a composition of Fe8L2D2AcO(OH)19 where L denotes the lactiobionate ion, D stands for one glucopyranose unit of dextrane and Ac is the acetate ion. Iron(III) acetate is the starting material in the preparation of the complex. The acetate neutralises the protons liberated in the interaction of iron(III) and the ligands and the acetic acid formed in this reaction is removed by steam distillation. An aqueous solution of 1.8 mol dm−3 iron concentration was prepared which has an osmotic pressure below 300 mosmol.

pH-metric, visible, UV and ESR spectral studies of the copper(II)-DL-3,4-dihydroxyphenylalanine (DL-DOPA) and the copper(II)-aminoacid-pyrocatechol systems were used to draw conclusions on the complexes formed in the copper(II)-DOPA system. The stability constants of these complexes were determined from the pH-metric data. It was found that at lower pH( 2 A and Cu(H 2 A) 2 are formed, while at higher pH values (>9) the pyrocatechol type complex Cu(HA) 2 and its deprotonated species are formed. In the intermediate pH range cyclic and open-chain dimeric species are produced, together with a complex containing both N,O and O,O bonds. The existence of this complex is also supported by the fact that formation of the mixed ligand complex is favoured in the copper(II)-pyrocatechol-alanine and copper(II)-pyrocatechol-phenylalanine systems.

Reaction of TiCl 3 ·3thf [thf = tetrahydrofuran) with β-diketones gives the complexes dichloro-β diketonatobis(tetrahydrofuranato)titanium(III). The spectroscopic and magnetic properties of the complexes have been investigated. Their e.p.r. spectra indicate structures with cis -chlorines and cis -thf ligands.

The stability constants of some different diamine-diamine and diamine-glycine nickel(II) and zinc(II) mixed ligand complexes have been determined pH-metrically. The formation enthalpies of the nickel(II) complexes were measured calorimetrically. It was found that the higher the difference between the log K 1 /K 2 values of the parent complexes, the higher the stability of the mixed complexes. Thermodynamic and spectral parameters of the nickel(II) complexes revealed that mixed ligand complex formation will be unfavourable if five-membered and six-membered chelate rings are simultaneously involved in the coordination sphere.

Addition of hydroxyphenyl derivatives to tris(dipicolinate)Tb(III) results in the generation of optical activity within the Tb(III) spectroscopic transitions. Unlike earlier work, in many cases the bonding was found not to be totally outer-sphere in nature, but the adducts could be best described as 1:1 Tb(DPA) 3− 3 /substrate complexes. At low pH values the interactions appeared to be outer-sphere in nature, but ionization of the hydroxyphenyl group resulted in the formation of the inner-sphere complex. Presumably, one of the dipicolinates partially dissociates to permit bonding of the ionized hydroxyphenyl portion of the substrate. The chiral substrates examined during the course of this study were hydroxylphenylglycine, tyrosine, dihydroxyphenylalanine (L-DOPA), tyrosinol, noreinephedrine, and epinephrine.