Binding of biogenic and synthetic polyamines to β-lactoglobulin

The bindings of biogenic polyamines spermine (spm), spermidine (spmd) and synthetic polyamines 3,7,11,15-tetrazaheptadecane·4HCl (BE-333) and 3,7,11,15,19-pentazahenicosane·5HCl (BE-3333) with β-lactoglobulin (β-LG) were determined in aqueous solution. FTIR, UV-vis, CD and fluorescence spectroscopic methods as well as molecular modeling were used to determine the polyamine binding sites and the effect of polyamine complexation on protein stability and secondary structure. Structural analysis showed that polyamines bind β-LG via both hydrophilic and hydrophobic contacts. Stronger polyamine-protein complexes formed with synthetic polyamines than biogenic polyamines, with overall binding constants of K_spm-β-LG = 3.2(±0.6) × 10⁴ M⁻¹, K_spmd-β-LG = 1.8(±0.5) × 10⁴ M⁻¹, K_BE-333-β-LG = 5.8(±0.3) × 10⁴ M⁻¹ and K_{BE-3333-β-LG} = 6.2(±0.05) × 10⁴ M⁻¹. Molecular modeling showed the participation of several amino acids in the polyamine complexes with the following order of polyamine-protein binding affinity: BE-3333 > BE-333 > spermine > spermidine, which correlates with their positively charged amino group content. Alteration of protein conformation was observed with a reduction of β-sheet from 57% (free protein) to 55-51%, and a major increase of turn structure from 13% (free protein) to ∼21% in the polyamine-β-LG complexes, indicating a partial protein unfolding.     

Solution and solid state study of copper(II) ternary complexes containing amino acids of interest for brain biochemistry - 1: Aspartic or glutamic acids with methionine or cysteine

Four new ternary complexes of Cu(II) containing aspartic or glutamic acids and methionine or cysteine as ligands were studied both in solution and in solid state. The solution study was performed using potentiometry, UV-Vis spectroscopy, electron paramagnetic resonance (EPR) spectroscopy, and electrochemistry. The stability constants of the ternary complexes were determined by potentiometry. The order of the values for the stability constants was CuGluMet (complex 4) < CuAspMet (complex 2) < CuGluCys (complex 3) < CuAspCys (complex 1), with complex 1 ≈ complex 3 ? complex 2 ≈ complex 4. This behavior was confirmed by the electronic spectra, EPR parameters and cyclic voltammetry. The compounds were synthesized in the solid state and characterized by thermogravimetry as well as vibrational and EPR spectroscopy. The results found in solid state are in agreement with the data found in solution studies where methionine, aspartic and glutamic acids coordinate to the copper(II) ion using the nitrogen atom of the amino group and one oxygen atom of the carboxylate group and cysteine coordinates through the nitrogen and sulfur atoms. The EPR data suggest that the complexes are square planar and that the complexes with cysteine as one of the ligands have some distortion.     

Reactions of ketones with coordinated nitriles on β-diketonato ruthenium complexes leading to formation of compounds with new carbon-carbon bonds

The reactions of [Ru(acac)₂(CH₃CN)₂] with four ketones (acetone, ethyl methyl ketone, acetylacetone and monochloroacetone), and the reactions of [Ru(acac)₂(C₆H₅CN)₂] with two ketones (acetone and ethyl methyl ketone) yielded six novel compounds of β-ketiminato ruthenium complexes: [Ru(acac)₂(mhmk)], [Ru(acac)₂(ehmk)], [Ru(acac)₂(mAmk)], [Ru(acac)₂(mClmk)], Ru(acac)₂(mhbk)], and [Ru(acac)₂(ehbk)] (mhmk = 4-iminopentane-2-one mono anion, ehmk = 5-iminohexane-3-one mono anion, mAmk = 3-(1-iminoethyl)-2,4-pentanedione mono anion, mClmk = 3-chloro-4-imino-pentane-2-one mono anion, mhbk = 1-phenyl-1-iminobutane-3-one mono anion, ehbk = 1-phenyl-1-iminopentane-3-one mono anion). All the new complexes have been characterized by elemental analyses, ¹H NMR, MS and electronic spectral data. Crystal and molecular structures for the six β-ketimine complexes have been solved by single crystal X-ray diffraction studies. A mechanism involving the attack of ketones on the coordinated nitrile has been proposed. The electrochemical redox behavior of the β-ketimine complexes has been elucidated.     

Synthesis, characterization, and aqueous chemistry of cytotoxic Au(III) polypyridyl complexes

This work reports the synthesis, characterization, and aqueous chemistry of a series of cytotoxic [Au(polypyridyl)Cl₂]PF₆ complexes {(where polypyridyl = dipyrido[3,2-f:2′,3′-h] quinoxaline (DPQ), dipyrido[3,2-a:2′,3′-c] phenazine (DPPZ) and dipyrido[3,2-a:2′,3′-c](6,7,8,9-tetrahydro) phenazine (DPQC))}. The crystal structure of [Au(DPQ)Cl₂]PF₆ was determined as example of the series and exhibits the anticipated square planar geometry common for d⁸ coordination complexes. The crystals of the complex belong to the space group P2₁/n with a = 7.624(2) Å, b = 18.274(5) Å, c = 14.411(14) Å, β = 98.03(3)°, and Z = 4. In ¹H NMR studies of these compounds in the presence of aqueous buffer, all four complexes rapidly converted to the dihydroxy species [Au(polypyridyl)(OH)₂] in a stepwise fashion. However, the [Au(polypyridyl)]³⁺ fragment believed to impart cytotoxicity in human ovarian cancer cell lines (A2780) remained intact and appeared stable for days. It was also noted that these Au(III) complexes were readily reduced in the presence of the common biological reducing agents, reduced glutathione and sodium ascorbate. How solution and redox stability may affect the biological activity of these novel Au(III) complexes is discussed.     

Synthesis, crystallography, phosphorescence of platinum complexes coordinated with 2-phenylpyridine and a series of β-diketones

Metallocyclic platinum(II) complexes coordinating with 2-phenylpyridine (ppy) and a series of β-diketone ancillary O^∧O ligands, (ppy)Pt(acac), (ppy)Pt(ba), (ppy)Pt(dbm), and (ppy)Pt(tta) (acac = acetylacetone, ba = benzoylacetone, dbm = dibenzoylmethane, tta = thenoyltrifluoroacetone) were synthesized. The crystal structure, absorption, emission, quantum yield and phosphorescence life time were characterized. As the conjugative π system of the O^∧O ligand increases in the order acac < ba < dbm, or there is a group -CF₃to attract the electron density of the tta ligand, the quantum yield decreases in the order (ppy)Pt(acac) > (ppy)Pt(ba) > (ppy)Pt(dbm) > (ppy)Pt(tta) due to an energy back-flow from ppy to the O^∧O ligand, a trend also in contrast to the phosphorescence emission spectra and time decay (biexponentially, ∼0.7-13 μs).     

Lanthanide complexation with 1,3,5-triamino 2,4,6-trihydroxycyclohexane

The protonation constants of 1,3,5-triamino-2,4,6-trihydroxycyclohexane (taci), at 25 °C in I = 1.00 M (NaClO₄) were determined to be: pKa₁, 5.57 (0.08); pKa₂, 7.45 (0.02); pKa₃, 9.05 (0.04). The log of the stability constants, log β₃₀₂, at 25°C in I = 1.00 M (NaClO₄) for formation of were measured by potentiometry to be: Nd(III), 25.33 (0.09); Eu(III), 26.42 (0.06); Tm(III), 30.07 (0.10); Lu(III), 33.68 (0.07) ; Y(III), 28.59 (0.07). ¹H NMR spectra were consistent with formation of a single complex from pcH 6 to 10. Laser fluorescence measurements of the ⁷F_o-⁵D_o transition of Eu(III) complexed by taci indicated a single complexed species. The shift in this peak relative to that of Eu³⁺(aq) was significantly greater than the values reported for the complexes of other organic ligands with Eu(III). Luminescence lifetime measurements indicated two water molecules bound to each of the Eu(III) cations in the taci complex.     

Aminoacid-derivatised picolinato-oxidovanadium(IV) complexes: Characterisation, speciation and ex vivo insulin-mimetic potential

The proligands PicMe-AaR (PicMe = methoxipicolyl-5-amide, where the amide substituent is an amino acid AaR = HisH, HisMe, IleH, IleMe, TrpH, TrpMe, HTyrEt, tBuTyrMe, HThrMe, tBuThrMe) and the complexes [VO(Pic-AaR)₂] have been synthesised and characterised. A detailed EPR study of the VO²⁺/Pic-His systems in water revealed the predominance of the complex [VO(Pic-His)H₂O] in the pH range 2-6, with tridentate coordination of Pic-His via the picolinate moiety and imidazole-Nδ. Speciation analyses of the binary systems VO²⁺/Pic-Aa (Aa = His, Ile, Trp) and the ternary systems VO²⁺/Pic-Aa/B (Aa = His, Ile; B = citrate (cit), lactate (lac), phosphate) showed a predominance of the ternary complexes [VO(Pic-Aa)(cit/lac)] and [VO(Pic-Aa)(cit/lac)OH]⁻ in the physiological pH regime. If, in addition, human serum albumin (HAS) and apotransferrin (Tf) are present, with all of the low and high molecular mass constituents in their blood serum concentrations, about two thirds of VO²⁺ is bound to the protein, while there is still a sizable amount of ternary complex [VO(Pic-Aa)(cit/lac)] present (about 1/4 for Pic-His and 1/3 for Pic-Ile) when the vanadium(IV) concentration is relatively high; at lower concentrations Tf is the predominant binder. Insulin-mimetic studies for VO²⁺/Pic-Aa (Aa = His, Ile, Tyr and Trp), based on a lipolysis assay with rat adipocytes, provided IC₅₀ values of 0.41(1) for VO²⁺/Pic-His and VO²⁺/Pic-Ile, which compares with 0.87(17) for VOSO₄.     

Crystal structures and spectroscopic properties of palladium complexes isolated from Pd-EDTA solutions

Two complexes were isolated from aqueous Pd(NO₃)₂-Na₂H₂EDTA solutions and studied by single crystal X-ray diffraction, IR/Raman spectroscopy, and photoelectron spectroscopy. The first complex, Pd(Hkpda)₂ (kpda = ketopiperazinediacetate dianion, C₈H₁₀N₂O₅), forms yellow parallelepipeds during slow evaporation of Pd(NO₃)₂-Na₂H₂EDTA solution at 25 °C, and is a result of EDTA oxidation. The second one, [Pd(μ-H₂EDTA)]₂ · 2NaNO₃ · 7.5H₂O, with two EDTA molecules acting as bridges between two palladium atoms, forms yellow bipyramides during fast evaporation at 60 °C. In both complexes, the palladium atoms adopt a planar trans-geometry by bonding to two nitrogen and two oxygen atoms of two ligand molecules.     

Synthesis, crystal structure and action on Escherichia coli by microcalorimetry of copper complexes with 1,10-phenanthroline and amino acid

Copper complexes: [Cu(phen)(L-Ser)(H₂O)Cl] (1), [Cu(phen)(Gly)(H₂O)]Cl·3H₂O (2), [Cu(phen)(L-Ala)(H₂O)]Cl·H₂O (3), [Cu(phen)(L-Phe)(H₂O)]Cl·2.5H₂O (4), Cu(phen)₂Cl₂·6H₂O (5) (phen = 1,10-phenanthroline) were synthesized and characterized. The structure of 1 was characterized by X-ray crystallography and showed in a triclinic system with space group P1, a = 6.8953(15) Å, b = 10.737(2) Å, c = 11.894(3) Å, α = 110.395(3)°, β = 94.183(4)° and γ = 100.540(3)°. The antibacterial activities on Escherichia coli (E. coli) of these five copper complexes and CuCl₂ (6) were investigated by microcalorimetry. By analyzing the obtained metabolic thermogenic data and curves, crucial parameters such as rate constant of bacterial growth (k), half inhibitory concentration (IC₅₀), and generation time (t_G) were determined. All these copper complexes could stimulate the growth of the E. coli at their lower concentration. At their higher concentration they all showed antibacterial action. The inhibition on E. coli was 5 > 1 ≈ 2 ≈ 3 ≈ 4 > 6. And the antibacterial mechanism was discussed preliminarily.     

Non-cyclopentadienyl zirconium complexes as catalysts for 1-hexene polymerization

The new β-diketonate complexes (hfac)₂ZrCl₂, (hfac)₃ZrCl, hfac = hexafluoroacetylacetonate, and (thd)₂ZrCl₂, thd = 2,2,6,6-tetramethyl-3,5-heptanedionate, have been prepared in good yield by reacting the corresponding β-diketonate thallium complexes with ZrCl₄ in stoichiometric amounts and they have been characterized by elemental analyses and NMR spectra.These complexes and the β-diketonate complexes (acac)₂ZrCl₂, (acac)₃ZrCl and (thd)₃ZrCl have been tested as catalysts in the polymerization of 1-hexene in the presence of N,N′-(dimethylanilinium)-tetrakis(pentafluorophenylborate) or ethyltrichloroacetate as co-catalysts at room temperature using ethyl aluminum sesquichloride as scavenger.     

Syntheses, structures and antimicrobial activities of various metal complexes of hinokitiol

Metal-oxygen bonding complexes (M = Mg^II, Mn^II, Ni^II, Mo^VI, W^VI, Pd^II, Sb^III, Bi^III, Fe^III, Ti^IV, K^I, Ba^II, Zr^IV and Hf^IV) with a hinokitiol (Hhino; 2-hydroxy-4-isopropylcyclohepta-2,4,6-trienone or β-thujaplicin) ligand, which has two unequivalent oxygen donor atoms, were synthesized and characterized by elemental analysis, TG/DTA, FT-IR and solution (¹H and ¹³C) NMR spectroscopy. Single-crystal X-ray structure analysis revealed various molecular structures for the complexes, which were classified into several families of family, i.e. type A [M^II(hino)₂(L)]₂ (M = Mg^II, Mn^II, Ni^II; L = EtOH or MeOH), with a dimeric structure consisting of one bridging hino⁻ anion, one chelating hino⁻ anion and one alcohol or water molecule, type B, with the octahedral, cis-dioxo, bis-chelate complexes cis-[M^VIO₂(hino)₂] (M = Mo^VI, W^VI), type C, with square planar complex [M^II(hino)₂] (M = Pd^II), type D, with tris-chelate, 7-coordinate complexes with one inert electron pair [M^III(hino)₃] (M = Sb^III, Bi^III), type D′, with the bis-chelate, pseudo-6-coordinate complexes with one inert electron pair [M^III(hino)₂X] (M = Sb^III, X = Br), type E, with tris-chelate, 6-coordinate complexes with Δ and Λ isomers [M^III(hino)₃] (M = Fe^III), type E′ of bis-chelate, 6-coordinate complex [M^IV(hino)₂X₂] (M = Ti^IV, X = Cl), type F, with water-soluble alkali metal salts [M^I(hino)] (M = K^I), and type H, with tetrakis-chelate, 8-coordinate complexes [M^IV(hino)₄](M = Zr^IV, Hf^IV). These structural features were compared with those of metal complexes with a related ligand, tropolone (Htrop). The antimicrobial activities of these complexes, evaluated in terms of minimum inhibitory concentration (MIC; μg mL⁻¹) in two systems, were compared to elucidate the relationship between structure and antimicrobial activity.     

Synthesis, crystal structures, DNA-binding properties, cytotoxic and antioxidation activities of several new ternary copper(II) complexes of N,N′-(p-xylylene)di-alanine acid and 1,10-phenanthroline

Three novel ternary copper(II) complexes, [Cu₂(phen)₂(l-PDIAla)(H₂O)₂](ClO₄)₂·2.5H₂O (1), [Cu₄(phen)₆(d,l-PDIAla)(H₂O)₂](ClO₄)₆·3H₂O (2) and [Cu₂(phen)₂(d,l-PDIAla)(H₂O)](ClO₄)₂·0.5H₂O (3) (phen = 1,10-phenanthroline, H₂PDIAla = N,N’-(p-xylylene)di-alanine acid) have been synthesized and structurally characterized by single-crystal X-ray crystallography and other structural analysis. Spectrometric titrations, ethidium bromide displacement experiments, CD (circular dichroism) spectral analysis and viscosity measurements indicate that the three compounds, especially the complex 3, strongly bind to calf-thymus DNA (CT-DNA). The intrinsic binding constants of the ternary copper(II) complexes with CT-DNA are 0.89 × 10⁵, 1.14 × 10⁵ and 1.72 × 10⁵ M⁻¹, for 1, 2 and 3, respectively. Comparative cytotoxic activities of the copper(II) complexes are also determined by acid phosphatase assay. The results show that the ternary copper(II) complexes have significant cytotoxic activity against the HeLa (Cervical cancer), HepG2 (hepatocarcinoma), HL-60 cells (myeloid leukemia), A-549 cells (pulmonary carcinoma) and L02 (liver cells). Investigations of antioxidation properties show that all the copper(II) complexes have strong scavenging effects for hydroxyl radicals and superoxide radicals.     

Synthesis, characterization, interaction with DNA and cytotoxicity in vitro of dinuclear Pd(II) and Pt(II) complexes dibridged by 2,2'-azanediyldibenzoic acid

The dinuclear complexes [Pd₂(L)₂(bipy)₂] (1), [Pd₂(L)₂(phen)₂] (2), [Pt₂(L)₂(bipy)₂] (3) and [Pt₂(L)₂(phen)₂] (4), where bipy = 2,2′-bipyridine, phen = 1,10-phenanthroline and L = 2,2′-azanediyldibenzoic dianion) dibridged by H₂L ligands have been synthesized and characterized. The binding of the complexes with fish sperm DNA (FS-DNA) were investigated by fluorescence spectroscopy. The results indicate that the four complexes bound to DNA with different binding affinity, in the order complex 4 > complex 3 > complex 2 > complex 1, and the complex 3 binds to DNA in both coordination and intercalative mode. Gel electrophoresis assay demonstrates the ability of the complexes to cleave the pBR 322 plasmid DNA. The cytotoxic activity of the complexes was tested against four different cancer cell lines. The four complexes exhibited cytotoxic specificity and significant cancer cell inhibitory rate.     

Complexation thermodynamics and the structure of the binary and the ternary complexes of Am, Cm and Eu with IDA and EDTA + IDA

The stability and the associated thermodynamic parameters of the binary and the ternary complexes of trivalent Am, Cm, and Eu with IDA and with EDTA + IDA, were determined by using a solvent extraction technique for aqueous solutions of I = 6.60 m (NaClO₄) at temperatures of 0-60 °C. The endothermic enthalpy and the positive entropy reflect the significant effect of dehydration in the formation of these complexes at high ionic strength. TRLFS and NMR (¹H and ¹³C) data helped to establish the structure of the ternary complexes in solution. In the ternary complex M(EDTA)(IDA)³⁻, EDTA binds via four carboxylates and two nitrogens, and IDA via two carboxylates and one nitrogen to the central Eu³⁺.     

Transition metal complexes (M = Cu, Ni and Mn) of Schiff-base ligands: Syntheses, crystal structures, and inhibitory bioactivities against urease and xanthine oxidase

Six new transition metal complexes (M = Cu(II), Ni(II) and Mn(III)) of tridentate (H₂L¹, HL²) and/or bidentate (HL³, HL⁴) Schiff-base ligands, obtained from the condensation of salicylaldehyde with glycine, N-(2-aminoethyl)morpholine, 4-(2-aminoethyl)phenylic acid and 4-(2-aminoethyl)benzsulfamide, respectively, were synthesized and structurally determined by single-crystal X-ray analysis. Complexes 1-6 were evaluated for their effect on the jack bean urease and xanthine oxidase (XO). Copper(II) complexes 1-3 (IC₅₀ = 0.43-2.25 μM) showed potent inhibitory activity against jack bean urease, comparable with acetohydroxamicacid (IC₅₀ = 42.12 μM), which is a positive reference. And these copper(II) complexes (IC₅₀ = 10.26-15.82 μM) also exhibited strong ability to inhibit activity of XO, comparable to allopurinol (IC₅₀ = 10.37 μM), which was used as a positive reference. Nickel(II) and manganese(III) complexes 4-6 showed weak inhibitory activity to jack bean urease (IC₅₀ = 4.36-8.25 μM) and no ability to inhibit XO (IC₅₀ > 100 μM).     

Synthesis and structure of platinum(II) complexes containing an asymmetric chelating diamine 2-morpholinoethylamine as the carrier

A series of novel platinum(II) complexes involving an asymmetric chelating diamine 2-morpholinoethylamine (MPEA) as the carrier, cis-[Pt(MPEA)X₂] (X₂ = 2Cl⁻, oxalate, malonate, 1,1-cyclobutanedicarboxylate (CBDCA), 3-hydroxy-1,1-cyclobutanedicarboxylate (HO-CBDCA)), have been synthesized and characterized by elemental analysis and spectroscopic data along with X-ray crystal structure for a representative complex cis-[Pt(MPEA) (CBDCA)]. The Pt(II) is in a square planar environment and is coordinated by a chelating CBDCA and MPEA in cis position. The complexes with dicarboxylate are quite soluble (>25 mg/ml) and stable in water. The cytotoxicity of the complexes has been assessed in the human lung cancer cell lines A549 and A549/ATCC. One complex, cis-[Pt(MPEA)Cl₂], is more active than carboplatin against both the sensitive and resistant cells, and has less cross-resistance with cisplatin.     

Synthesis, spectroscopic characterization and structural studies of mixed ligand complexes of Sr(II) and Ba(II) with 2-hydroxybenzophenone and salicylaldehyde, hydroxyaromatic ketones or β-diketones: Crystal structure of 2-HOC6H4C(O)C6H5

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.     

N,O versus O,O coordination in β-imino diketonato complexes: Role of the metal center and of the imino substituent

β-Imino carbonyl enolato metal(II) complexes of general formula [M((RCO)(R′CO)CC(R″)NH)₂] (M = Mn, Fe, Co, Ni, Cu, Zn, Pd, R = R′ = Me, R″ = CCl₃; M = Cu, Pd, R = R′ = Me, R″ = PhCO; R = Me, R′ = Ph, R″ = PhCO; R = R′ = Ph, R″ = PhCO) are easily synthesized by the reaction of metal(II) acetates with the proper β-enaminodiones in 1/2 molar ratio in ethanol at room temperature. In all the cases the trifunctional NOO β-imino carbonyl enolate ligand acts as bidentate to give ML₂ complexes, whose structure depends on the metal center and on the nature of the substituent R″ at the imino carbon. With R″ = CCl₃ an O,O coordination is observed for all the metal centers but one, in fact palladium(II) exhibits an N,O coordination through the imino nitrogen and one keto oxygen. By contrast with R″ = PhCO the ligand is always coordinated through the imino nitrogen and one keto oxygen atom.     

Can geometry control the coordination behaviour of 2-hydroxy-1-naphthaldehyde-N(4)-phenylthiosemicarbazone? A study towards its origin

2-Hydroxy-1-naphthaldehyde-N(4)-phenylthiosemicarbazone [H₂-Nap-ptsc] (H₂L) was reacted with square planar complexes of the type [MCl₂(EPh₃)₂] (where M = Ni or Pd; E = P or As) and octahedral [RuHCl(CO)(PPh₃)₃]. Square planar complexes ([Ni(Nap-ptsc)PPh₃)]; [Pd(Nap-ptsc)PPh₃)]; [Pd(Nap-ptsc)AsPh₃)]) gave products with only ONS tri coordinated thiosemicarbazone whereas octahedral ruthenium complex gave two products, one with NS and the other with ONS coordination. It is interesting to note that NS bi coordination leads to the formation of more strained four member ring. All the new complexes have been characterised by analytical, spectral, crystallographic and electrochemical methods.     

Synthesis, spectroscopy, structure and photophysical properties of dinaphthylmethylarsine complexes of palladium(II) and platinum(II)

Dinaphthylmethylarsine complexes of palladium(II) and platinum(II) with the formulae [MX₂L₂] (M = Pd, Pt; L = di(1-naphthyl)methylarsine = Nap₂AsMe and X = Cl, Br, I), [M₂Cl₂(μ-Cl)₂L₂], [PdCl(S₂CNEt₂)L], [Pd₂Cl₂(μ-OAc)₂L₂] and [MCl₂(PR₃)L] (PR₃ = PEt₃, PPr₃, PBu₃, PMePh₂) have been prepared. These complexes have been characterized by elemental analyses, IR, Raman, NMR (¹H, ¹³C, ³¹P) and UV-vis spectroscopy. The stereochemistry of the complexes has been deduced from the spectroscopic data. The crystal structures of trans-[PdCl₂(PEt₃)(Nap₂AsMe)] and of [Pd(S₂CNEt₂)₂], a follow-up product, were determined. The UV-vis spectra of [MX₂L₂] complexes show a red shift on going from X = Cl to X = I. The complexes [PdX₂L₂] and [PtX₂L₂] are strongly luminescent in fluid solution and in the solid at ambient temperature.