Syntheses, crystal structures, spectroscopic, fluorescence and thermal properties of silver(I) 5,5-diethylbarbiturato complexes with some aminopyridines

Three new silver(I) complexes of 5,5-diethlybarbiturate (barb), [Ag(barb)(apy)]·H₂O (1), {[Ag(μ-ampy)][Ag(μ-barb)₂]}_n (2) and [Ag(barb)(dmamhpy)] (3) [apy = 2-aminopyridine, ampy = 2-aminomethylpyridine and dmamhpy = 2-(dimethylaminomethyl)-3-hydroxypyridine] have been synthesized and characterized by elemental analysis and FT-IR. Single crystal X-ray diffraction analyses showed that complexes 1 and 3 are mononuclear. In 1, the silver(I) ion is linearly coordinated by a barb anion and a ampy ligand, while a bidentate dmamhpy ligand together with an N-coordinated barb anion forms a trigonal coordination geometry around silver(I) in 3. Complex 2 is a one-dimensional coordination polymer in which silver(I) ions are bridged by ampy ligands, leading to a cationic chain . The [Ag(barb)₂]⁻ units contains two N-bonded barb ligands, bridging the silver centers in the cationic and anionic units via the carbonyl O atoms. Thus, complex 2 contains two-coordinated and four-coordinated silver ions. All complexes display hydrogen-bonded network structures and exhibit appreciable fluorescence at room temperature. Thermal analysis (TG-DTA) data are in agreement with the structures of the complexes.     

Synthesis and transition metal complexes of 3,3-bis(1-vinylimidazol-2-yl)propionic acid, a new N,N,O ligand suitable for copolymerisation

The new N,N,O heteroscorpionate ligand 3,3-bis(1-vinylimidazol-2-yl)propionic acid (Hbvip) (5) was synthesised in five steps starting from 1-vinylimidazole. This ligand is closely related to 3,3-bis(1-methylimidazol-2-yl)propionic acid (Hbmip), but contains two vinyl linker groups which can be used for radical-induced polymerisation reactions. The κ³-N,N,O coordination behaviour of 5 was proven by the synthesis of the tricarbonyl complexes [Re(bvip)(CO)₃] (6), [Mn(bvip)(CO)₃] (7) and [Cu(bvip)₂] (8). To obtain good yields of 6, it was synthesised in water instead of THF. The ligand as well as all three complexes were characterised by X-ray crystallography. Copolymerisation of 5 with pure methyl methacrylate (MMA) or a combination of MMA and ethylene glycol dimethacrylate (EGDMA) led to the solid phases P1 and P2. Polymer-bound rhenium and manganese tricarbonyl complexes could be obtained by the reaction of deprotonated P1 with [MBr(CO)₅] (M = Re, Mn) and also by copolymerisation of 6 and 7 with MMA. In both cases, the facial tripodal binding behaviour was evidenced by IR spectra of the polymers. Furthermore, the content of metal incorporated in the polymers was determined by elemental analysis, AAS or ICP-OES measurements. Reaction of the deprotonated solid phase P1 with copper(II) chloride led to a blue solid-phase (P1-Cu). The UV-Vis absorption maximum of P1-Cu is found at 615 nm, which is almost identical to that found for 8. Thereby, it seems likely that P1 is flexible enough to form bisligand complexes with copper(II). This means that the copper centres act as a kind of crosslinking agents. In contrast, the heterogeneous reaction of P2 with copper(II) chloride yielded a lime green solid phase (P2-Cu). The bathochromic shift of the absorption maximum by 102 nm suggests one-sided bound copper centres.     

β-Diiminatolanthanoid(III) halides revisited

The crystalline compounds [LnCl₂(L)(thf)₂] [Ln = Ce (1), Tb (2), Yb (3)], [NdI₂(L)(thf)₂] (4), [LnCl(L′)₂] [Ln = Tb (5), Yb (6) (a known compound)] and [YbCl(L′′)(μ-Cl)₂Li(OEt₂)₂] (7) have been prepared [L = {N(C₆H₃Prⁱ₂-2,6)C(H)}₂CPh, L′ = {N(SiMe₃)C(Ph)}₂CH, L′′ = {N(SiMe₃)C(C₆H₄Ph-4)}₂CH]. The X-ray molecular structures of 2-7 have been established; in each, the monoanionic ligand L, L′ or L′′ is N,N′-chelating and essentially π-delocalised. Each of 1-7 was prepared from the appropriate LnCl₃, or for 4 [NdI₃(thf)₂], and an equivalent portion of the appropriate alkali metal [Li for 7, Na for 2, 3 and 5, or K for 1, 4 and 6] β-diiminate in thf; the isolation of exclusively 5 and 6 (rather than the L′ analogues of 2 or 3) is noteworthy, as is the structure of 7 which has no precedent in Group 3 or 4f metal β-diiminato chemistry.     

Crystal structures and third-order NLO properties in DMF solution of Co(II)-bpfp coordination polymers (bpfp=N,N-bis(pyridylformyl)piperazine)

Two novel Co(II) coordination polymers {[Co(H₂O)₂(CH₃OH)₂(4-bpfp)](NO₃)₂}_n1 (4-bpfp=N,N^′-bis(4-pyridylformyl)piperazine) and [Co(NCS)₂(CH₃OH)₂(3-bpfp)]_n2 (3-bpfp=N,N^′-bis(3-pyridylformyl)piperazine) have been synthesized and characterized by single crystal X-ray diffraction. Both the polymers consist of one-dimensional chains constructed by bridging bpfp ligands and Co(II) ions. The existence of O?H-O hydrogen bond in 1 and S?H-O hydrogen bond in 2 play important roles in creating interesting supramolecular structures. Their third-order nonlinear optical (NLO) properties in DMF solution have been studied by Z-scan technique. The results reveal that polymers 1 and 2 exhibit strong NLO absorption effects (α₂=9.00×10⁻¹¹ m W⁻¹ for 1; 1.41 × 10⁻¹⁰ m W⁻¹ for 2) and self-focusing performance (n₂=3.24×10⁻¹⁶ esu for 1; 3.05 × 10⁻¹⁶ esu for 2) in DMF solutions. The corresponding effective NLO susceptibilities χ⁽³⁾ values are 3.08 × 10⁻¹² esu (1) and 4.70 × 10⁻¹² esu (2). All of the values are comparable to those of the reported good NLO materials. Additionally, the TG-DTA results of the two polymers are in agreement with the crystal structures.     

Design of a flexible ligand for the construction of a one-dimensional metal-organic coordination polymer

A new ligand LH (where LH = N-(picolinoyl)-biurate) has been prepared and characterized. The presence of three amide linkages make this ligand sufficiently flexible to act as N,N,O donor tridentate blocking ligand in the formation of a one dimensional metal-ligand layer like structure. Reaction of LH and dicyanamide (dca) with Co(NO₃)₂ · 6H₂O gives [CoL(dca)]_n (1). In this compound picolinamide modulated ligand L coordinated the central Co(II) ion in a meridonal-fashion. The single crystal X-ray crystallography revealed that in 1, dca acts as μ_1,5− singly bridging ligand whereas μ_1,5− doubly bridging is the more common type. This gives rise to the 1D undulated waves like structure. The Co(II) centre is surrounded in a distorted square pyramidal coordination geometry. The variable temperature magnetic (VTM) susceptibility measurements show that the global feature of the χ_MT versus T curve for 1 is characteristic of very weak antiferromagnetic interactions through the dicyanamide ligand and between 300 and 5 K the best fit parameter was determined as J = −3.52 cm⁻¹. The X-ray structure, VTM study and UV-Vis spectrum of the compound show that 1 is a low-spin square-pyramidal compound whereas high-spin compounds are more common for the five coordinated cobalt (II) compounds. The X-band EPR spectrum of 1 at room temperature shows only one isotropic band centred at g = 2.08.     

Formation of coordination polymer and molecular complex of 4,4′-bipyridyl-N,N′-dioxide of manganese and zinc

A 1D-coordination polymer [{Mn₃(C₆H₅COO)₆(BPNO)₂(MeOH)₂}(MeOH)₂]_n (1) having benzoate as the anionic ligand and 4,4′-bipyridyl-N,N′-dioxide (BPNO) as bridging ligand is synthesized by reacting benzoic acid with manganese(II) acetate tetrahydrate followed by reaction with 4,4′-bipyridyl-N N′-dioxide. The bridging bidentate BPNO ligands in this coordination polymer along with the benzoate bridges hold the repeated units. The chain like structure in one dimension by benzoate bridges are connected to each other through the μ³-η²:η¹ bridges of BPNO ligands. This coordination polymer can be transformed to a molecular complex [Mn(H₂O)₆](C₆H₅COO)_2.4BPNO (2). In this complex the BPNO remains outside the coordination sphere but they are hydrogen bonded to water molecules to form self assembled structure. The reaction of 3,5-pyrazoledicarboxylic acid (L₁H2) and BPNO with manganese(II) acetate or zinc(II) acetate led to molecular complexes with composition [M₂(L₁)₂(H₂O)₆].BPNO·xH₂O {where M = Mn(II) (3), Zn(II)(4)}. These molecular complexes of BPNO are characterised by X-ray crystallography. The complexes 3-4 are binuclear carboxylate complexes having M₂O₂ core formed from carboxylate ligands with two metal ions.     

Synthesis and characterization of platinum(IV) complexes with N,S and S,S heterocyclic ligands

The reactions of [PtMe₃(OAc)(bpy)] (4) with the N,S and S,S containing heterocycles, pyrimidine-2-thione (pymtH), pyridine-2-thione (pytH), thiazoline-2-thione (tztH) and thiophene-2-thiol (tptH), resulted in the formation of the monomeric complexes [PtMe₃(-κS)(bpy)] ( = pymt, 5; pyt, 6; tzt, 7; tpt, 8), where the heterocyclic ligand is coordinated via the exocyclic sulfur atom. In contrast, in the reactions of [PtMe₃(OAc)(Me₂CO)_x] (3, x = 1 or 2) with pymtH, pytH, tztH and tptH dimeric complexes [{PtMe₃(μ-)}₂] (μ- = pymt, 9; pyt, 10; tzt, 11) and the tetrameric complex [{PtMe₃(μ₃-tpt-κS)}₄] (12), respectively, were formed. The complexes were characterized by microanalyses, ¹H and ¹³C NMR spectroscopy and negative ESI-MS (12) measurements. Single-crystal X-ray diffraction analysis of [PtMe₃(pymt-κS)(bpy)] (5) exhibited a conformation where the pymt ligand lies nearly perpendicular to the complex plane above the bpy ligand that was also confirmed by quantum chemical calculations on the DFT level of theory.     

Magnetic and structural studies of novel tetranickel hydroxamates

The dinickel(II) compound [Ni₂(μ-OAc)₂(OAc)₂(μ-H₂O)(asy·dmen)₂]·2.5H₂O, 1; undergoes facile reaction in a 1:2 molar ratio with benzohydroxamic acid (BHA) in ethanol to give the novel nickel(II) tetranuclear hydroxamate complex [Ni₄(μ-OAc)₃(μ-BA)₃(asy·dmen)₃][OTf]₂·H₂O, 2, in which the bridging acetates, bridging two nickel atoms in 1, undergo a carboxylate shift from the μ₂-η¹:η¹ bridging mode of binding to the μ₃-η¹:η² bridging three nickel atoms in the tetramer. The structure of complex 2 was determined by single-crystal X-ray crystallography. The two monodentate acetates, water and two bidentate bridging acetates of two moles of complex 1 are replaced by three monodentate bridging acetates and three benzohydroxamates. Three nickel atoms in the tetramer, Ni(2), Ni(3) and Ni(4) are in a N₂O₄ octahedral environment, while the fourth nickel atom Ni(1) is in an O(6) octahedral environment. The Ni-Ni separations are Ni(1)-Ni(2) = 3.108 Å, Ni(1)-Ni(3) = 3.104 Å and Ni(1)-Ni(4) = 3.110 Å, which are longer than previously studied in dinuclear urease inhibited models but shorter than in the nickel(II) tetrameric glutarohydroxamate complex [Ni₄(μ-OAc)₂(μ-gluA₂)₂(tmen)₄][OTf]₂, isolated and characterized previously in this laboratory. Magnetic studies of the tetrameric complex show that the four Ni(II) ions are ferromagnetically coupled, leading to a total ground spin state S_T = 4. Three analogous tetranuclear nickel hydroxamates were prepared from AHA and BHA and the appropriate dinuclear complex with either sy·dmen or asy·dmen as capping ligands.     

Towards absolute asymmetric synthesis. Synthesis and crystal structure of stereochemically labile MCl2 (M = Co, Ni, Cu, Zn) complexes with diamine ligands

In search for new conglomerates, seven stereochemically labile complexes between MCl₂ (M = Co, Cu, Ni, Zn) and bidentate ligands, the commercially available N,N,N′-trimethylethane-1,2-diamine (trimeda) and the somewhat bulkier N-isopropyl-N,N′,N′-trimethylethane-1,2-diamine (itmeda), have been synthesized and characterized using single crystal X-ray diffraction. The trimeda and itmeda ligands exhibit chirogenic nitrogen centers and may form chiral metal complexes that are candidates for total spontaneous resolution. Copper(II) chloride forms the dimeric meso complexes [{CuCl₂(trimeda)}₂] (1) and [{CuCl₂(itmeda)}₂] (2), while [CoCl₂(trimeda)₂] (3) and [NiCl₂(trimeda)₂] (4) exhibit six-coordinate but chiral (R,R)- and (S,S)-complexes. Three examples of the chiral target complex, comprising four-coordinate stereochemically labile monomers, was successfully prepared, viz. [NiCl₂(itmeda)] (5), [ZnCl₂(itmeda)] (6), and [CoCl₂(itmeda)] (7).In all seven complexes, the λ-conformation of the five-membered trimeda-metal chelate ring corresponds to the (S)-configuration at nitrogen, and vice versa. Supramolecular interactions in 3 and 4 form hydrogen-bonded heterochiral ribbons. However, crystals of 5-7 display homochiral interactions resulting in polar phases. Weak CH-Cl interactions in 5 and 6 form homochiral layers. In 7, interactions form homochiral helices along the a-axis.     

Syntheses and 1D structures of organic-inorganic hydrid polymers combining M(ClO4)2 (M = Cd, Zn) junctions and the semi-flexible bis-pyridyl ligand 3-pmpmd (N,N′-bis(3-pyridylmethyl)pyromellitic diimide)

Two 1D organic-inorganic coordination polymers, [Cd(3-pmpmd)(CH₃CN)₂(H₂O)₂]_n · 2n(ClO₄)₂ (1) and [Zn(3-pmpmd)_1.5(H₂O)₂]_n · 2n(ClO₄)₂ · nCH₃CN (2), were obtained from M(ClO₄)₂ (M = Cd, Zn) and the semi-flexible 3,3′-N-donor bis-pyridyl ligand 3-pmpmd: 1 has an 1D zigzag framework with 3-pmpmd in the Z_T-mode (anti, trans-) conformation, while 2 has an 1D rod and loop network with 3-pmpmd in both Z_T- and Z_C-mode (anti, cis-) conformations. Results showed that the metal ions could influence the coordination mode of a semi-flexible bis-pyridyl ligand.     

Synthesis and structure determination of two new dinuclear end-to-end doubly bridged azido- and thiocyanato-copper(II) complexes derived from diethyldiethylenetriamine

Herein, we report the synthesis and characterization of two new dinuclear bridged azido and bridged thiocyanato complexes: [Cu₂(Et₂dien)₂(μ_1,3-N₃)₂](ClO₄)₂ (1) and [Cu₂(Et₂dien)₂(μ_N,S-NCS)₂]-(ClO₄)₂ (2) where Et₂dien = N,N-diethyldiethylenetriamine. In both complexes, the two copper centers are linked by two azide or two thiocyanate groups in end-to-end bonding fashion. The copper ions are penta-coordinated by three N-atoms of the Et₂dien ligand, one N atom from the bridging azido in 1 or from the thiocyanato group in 2. The fifth coordination site is occupied by N or S atom from the second bridging azide or thiocyanate ligand, respectively. The coordination geometry around the Cu(II) ions in the two complexes may be described as close to square pyramidal (SP) stereochemistry with severe distortion to trigonal bipyramidal (TBP) stereochemistry. The intradimer Cu?Cu distances are 5.264(1) and 5.571(1) Å for the azido and thiocyanato complex, respectively. The IR stretching frequencies of the azido, and the thiocyanato, ν(NCS⁻) groups in the 2030-2120 cm⁻¹ region are discussed in relation to other related species. The visible spectra of the complexes studied in different solvents reveal the assigned predominant SP stereochemistry in solution with the presence of a pronounced amount of TBP geometry in the thiocyanato complex. Moreover, the complexes undergo solvolysis through bond rupture and displacement of one of the bridged azido or thiocyanato ligands.     

The first iron(III) complexes with cyclin-dependent kinase inhibitors: Magnetic, spectroscopic (IR, ES+ MS, NMR, Fe Mössbauer), theoretical, and biological activity studies

The first Fe^III complexes 1-6 with cyclin-dependent kinase (CDK) inhibitors of the type [Fe(L_n)Cl₃]·nH₂O (n = 0 for 1, 1 for 2, 2 for 3-6; L₁-L₆ = C2- and phenyl-substituted CDK inhibitors derived from 6-benzylamino-9-isopropylpurine), have been synthesized and characterized by elemental analysis, IR, ⁵⁷Fe Mössbauer, ¹H and ¹³C NMR, and ES+ mass spectroscopies, conductivity and magnetic susceptibility measurements, and thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The study revealed that the compounds are mononuclear, tetrahedral high-spin (S = 5/2) Fe^III complexes with an admixture of an S = 3/2 spin state originating probably from five-coordinated Fe^III ions either connecting with a bidentate coordination mode of the CDK inhibitor ligand or relating to the possibility that one crystal water molecule enters the coordination sphere of the central atom in a portion of molecules of the appropriate complex. Nearly spin-only value of the effective magnetic moment (5.82 μ_eff/μ_B) was determined for compound 1 due to absence of crystal water molecule(s) in the structure of the complex. Based on NMR data and DFT calculations, we assume that the appropriate organic ligand is coordinated to the Fe^III ion through the N7 atom of a purine moiety. The cytotoxicity of the complexes was tested in vitro against selected human cancer cell lines (G-361, HOS, K-562 and MCF-7) along with the ability to inhibit the CDK2/cyclinE kinase. The best cytotoxicity (IC₅₀: 4-23 μM) and inhibition activity (IC₅₀: 0.02-0.09 μM) results have been achieved in the case of complexes 2-4, and complexes 3, 4 and 6, respectively. In addition, the X-ray structure of 2-chloro-6-benzylamino-9-isopropylpurine, i.e. a precursor for the preparation of L₁, L₄ and L₅, is also described.     

6-Halogenopyridin-2-olato complexes with the diruthenium(2+) core: Equilibria between head-to-head and head-to-tail structures

The dinuclear bis(6-X-pyridin-2-olato) ruthenium complexes [Ru₂(μ-XpyO)₂(CO)₄(PPh₃)₂] (X = Cl (4B) and Br (5B)), [Ru₂(μ-XpyO)₂(CO)₄(CH₃CN)₂] (X = Cl (6B), Br (7B) and F (8B)) and [Ru₂(μ-ClpyO)₂(CO)₄(PhCN)₂] (9B) were prepared from the corresponding tetranuclear coordination dimers [Ru₂(μ-XpyO)₂(CO)₄]₂ (1: X = Cl; 2: X = Br) and [Ru₂(μ-FpyO)₂(CO)₆]₂ (3) by treatment with an excess of triphenylphosphane, acetonitrile and benzonitrile, respectively. In the solid state, complexes 4B-9B all have a head-to-tail arrangement of the two pyridonate ligands, as evidenced by X-ray crystal structure analyses of 4B, 6B and 9B, in contrast to the head-to-head arrangement in the precursors 1-3. A temperature- and solvent-dependent equilibrium between the yellow head-to-tail complexes and the red head-to-head complexes 4A-7A and 9A, bearing an axial ligand only at the O,O-substituted ruthenium atom, exists in solution and was studied by NMR spectroscopy. Full ¹H and ¹³C NMR assignments were made in each case. Treatment of 1 and 2 with the N-heterocyclic carbene (NHC) 1-butyl-3-methylimidazolin-2-ylidene provided the complexes [Ru₂(μ-XpyO)₂(CO)₄(NHC)], X = Cl (11A) or Br (12A). An XRD analysis revealed the head-to-head arrangement of the pyridonate ligands and axial coordination of the carbene ligand at the O,O-substituted ruthenium atom. The conversion of 11A and 12A into the corresponding head-to-tail complexes was not possible.     

2D network coordination polymers of lanthanide with N-(2-pyridylmethyl)iminodiacetic acid: Hydrothermal syntheses, crystal structures and luminescent properties

Six lanthanide two-dimensional network coordination polymers with the general formula of [Ln(pmida)(NO₃)(H₂O)]_n, where Ln = La (1), Nd (2), Sm (3), Gd (4), Dy (5), Er (6) and pmida²⁻ = N-(2-pyridylmethyl)iminodiacetate, have been synthesized by hydrothermal process and characterized by elemental analysis, Infrared spectroscopy, thermogravimetric analysis and single-crystal X-ray diffraction. All crystals are isostructural and crystallize in the monoclinic space group P2₁/a. The lanthanide(III) ion is nine-coordinated in a geometry of distorted tricapped trigonal prism by two N atoms and two O atoms from one pmida²⁻ ligand, two bridging carboxylate O atoms from other two pmida²⁻ ligands, two O atoms of a bidentate chelating nitrate and a O atom of a coordinated water molecule. The luminescent properties of [Sm(pmida)(NO₃)(H₂O)]_n (3) and [Dy(pmida)(NO₃)(H₂O)]_n (5) were investigated.     

Aromatic N-oxide bridged copper(II) coordination polymers: Synthesis, characterization and magnetic properties

The complexes [Cu₂(o-NO₂-C₆H₄COO)₄(PNO)₂] (1), [Cu₂(C₆H₅COO)₄(2,2′-BPNO)]_n (2), [Cu₂(C₆H₅COO)₄(4,4′-BPNO)]_n (3), [Cu(p-OH-C₆H₄COO)₂(4,4′-BPNO)₂·H₂O]_n (4), (where PNO = pyridine N-oxide, 2,2′-BPNO = 2,2′-bipyridyl-N,N′-dioxide, 4,4′-BPNO = 4,4′-bipyridyl-N,N′-dioxide) are prepared and characterized and their magnetic properties are studied as a function of temperature. Complex 1 is a discrete dinuclear complex while complexes 2-4 are polymeric of which 2 and 3 have paddle wheel repeating units. Magnetic susceptibility measurements from polycrystalline samples of 1-4 revealed strong antiferromagnetic interactions within the {Cu₂}⁴⁺ paddle wheel units and no discernible interactions between the units. The complex 5, [Cu(NicoNO)₂·2H₂O]_n·4nH₂O, in which the bridging ligand to the adjacent copper(II) ions is nicotinate N-oxide (NicoNO) the transmitted interaction is very weakly antiferromagnetic.     

Synthesis, structure, cytotoxic activities and DNA-binding properties of tetracopper(II) complexes with dissymmetrical N,N′-bis(substituted)oxamides as ligands

To compare the cytotoxicities and the DNA-binding properties in tetranuclear complexes with different bridging ligands, two tetracopper(II) complexes with formulae of [Cu₄(oxbe)₂Cl₂(bpy)₂]·4H₂O (1) and [Cu₄(oxbm)₂Cl₂(bpy)₂]·2H₂O (2) were synthesized, where H₃oxbe and H₃oxbm stand for N-benzoato-N′-(2-aminoethyl)oxamide and N-benzoato-N′-(1,2-propanediamine)oxamide, respectively, and bpy is 2,2′-bipyridine. Complex 1 was characterized by elemental analyses, IR and electronic spectra and single-crystal X-ray diffraction. The crystal structure reveals the presence of the circular tetranuclear copper(II) cations which are assembled by a pair of cis-oxamido-bridged dinuclear copper(II) units through carboxyl bridges. The crystal structure of complex 2 has been reported in our previous paper. However, the bioactivities were not studied. Cytotoxicities experiments reveal that both the two complexes exhibit cytotoxic effects against human hepatocellular carcinoma cell SMMC-7721 and human lung adenocarcinoma cell A549, and complex 1 has the better activities than those of complex 2. The results of the interactions between the two complexes and herring sperm DNA (HS-DNA) suggest that the two complexes interact with HS-DNA in the mode of intercalation with the intrinsic binding constants of 3.93 × 10⁴ M⁻¹ (1) and 2.48 × 10⁴ M⁻¹ (2). These results indicated that the bridging ligands may play an important role in the cytotoxicities and the DNA-binding properties of tetranuclear complexes.     

Coordination versatility of 1,3-bis[3-(2-pyridyl)pyrazol-1-yl]propane: Co(II) and Ni(II) complexes

The ligand 1,3-bis[3-(2-pyridyl)pyrazol-1-yl]propane (L⁸) has afforded six-coordinate monomeric and dimeric complexes [(L⁸)Co^II(H₂O)₂][ClO₄]₂ (1), [(L⁸)Ni^II(MeCN)₂][BPh₄]₂ (2), [(L⁸)Ni^II(O₂CMe)][BPh₄] (3), and . The crystal structures of 1, 2 · MeCN, 3, and 4 revealed that the ligand L⁸ is flexible enough to expand its coordinating ability by fine-tuning the angle between the chelating fragments and hence folds around cobalt(II)/nickel(II) centers to act as a tetradentate chelate, allowing additional coordination by two trans-H₂O, cis-MeCN, and a bidentate acetate affording examples of distorted octahedral , , and coordination. The angles between the two CoN₂/NiN₂ planes span a wide range 23.539(1)° (1), 76.934(8)° (2), and 69.874(14)° (3). In contrast, complex 4 is a bis-μ-1,3-acetato-bridged (syn-anti coordination mode) dicobalt(II) complex [Co?Co separation: 4.797(8) Å] in which L⁸ provides terminal bidentate pyridylpyrazole coordination to each cobalt(II) center. To our knowledge, this report provides first examples of such a coordination versatility of L⁸. Absorption spectral studies (MeCN solution) have been done for all the complexes. Complexes 1-3 are uniformly high-spin. Temperature-dependent (2-300 K) magnetic studies on 4 reveal weak ferromagnetic exchange coupling between two cobalt(II) (S = 3/2) ions. The best-fit parameters obtained are: Δ (axial splitting parameter) = −765(5) cm⁻¹, λ (spin-orbit coupling) = −120(3) cm⁻¹, k (orbital reduction factor) = 0.93, and J (magnetic exchange coupling constant) = +1.60(2) m⁻¹.     

Synthesis, structures, luminescence/magnetic properties of complexes of the M/1-hydroxybenzotriazole, M = cobalt, nickel, silver, zinc and copper

Five novel complexes, Co(OBt)₂ · 7H₂O (1) (OBt = 1-hydroxybenzotriazole ion), Ni₃(OBt)₆ · 6H₂O (2), [Ag(OBt)(HOBt)]_n (3), [Zn(OBt)₂]_n (4) and [Cu₂(OBt)₄ · 3H₂O]_n (5) were synthesized by hydrothermal method and characterized by elemental analysis, IR spectroscopy, TGA, XRPD, and single-crystal X-ray diffraction. The results from single-crystal X-ray diffraction indicate that 1-5 are zero-dimensional (0D), zero-dimensional, one-dimensional (1D), and three-dimensional (3D) frameworks, respectively. In particular, 3 is twin crystal; 4 possesses of double-stranded chains; 5 crystallizes in orthorhombic space group P2₁2₁2₁ with a helical chain in its structure. The luminescence properties and the magnetic properties of the five complexes were investigated.     

Exploring the coordination chemistry and reactivity of hemilabile N-alkylaminopyrazole ligands towards Pd(II)

Reaction of the N-alkylaminopyrazole (NN′N) ligands bis[(3,5-dimethyl-1-pyrazolyl)methyl]ethylamine (bdmae) and bis[(3,5-dimethyl-1-pyrazolyl)methyl]isopropylamine (bdmai) with [PdCl₂(CH₃CN)₂] in a 1:1 M/L ratio in CH₂Cl₂ produces cis-[PdCl₂(NN′N)] (NN′N = bdmae (1), bdmai (2)). The solid state structure of complex 1 was determined by X-ray diffraction studies. The bdmae ligand is coordinated through the two N_pz atoms to the metal atom, which completes its coordination with two chlorine atoms in a cis disposition.Treatment of the corresponding ligand with [PdCl₂(CH₃CN)₂] in 1:1 M/L ratio in the presence of AgBF₄ and metathesis with NaBPh₄ in CH₂Cl₂/CH₃OH (3:1) gave [PdCl(bdmae)](BPh₄) (3), and in the presence of NaBPh₄ in CH₂Cl₂/CH₃CN (3:1) gave [PdCl(bdmai)](BPh₄) (4). Complexes 1 and 2 were again obtained when complexes 3 and 4 were heated under reflux in a solution of Et₄NCl in acetonitrile. These Pd(II) compounds were characterised by elemental analyses, conductivity measurements, IR, ¹H and ¹³C{¹H} NMR, HMQC and NOESY spectroscopies. The NMR studies of the complexes prove the rigid conformation of the ligands when they are complexed.     

Syntheses and characterization of titanium malonato and amino acid complexes: [Ti(cp)2(OOCCH2NMe2)] - The first structurally characterized α-amino acid titanium(III) complex

The reaction of [Ti(cp^∗)₂(BTMSA)] (1) (cp^∗ = η⁵-C₅Me₅, BTMSA = bis(trimethylsilyl)acetylene) with malonic acids ((HOOC)₂CR₂, R = H, Me) and N,N-dimethylglycine resulted in the formation of titanium(IV) dicarboxylato complexes [Ti(cp^∗)₂{(OOC)₂CR₂}] (R = H, 2; R = Me, 3) and an α-amino acid titanium(III) complex [Ti(cp^∗)₂(OOCCH₂NMe₂)] (4). The identities of complexes 2-4 were confirmed by microanalysis, ¹H and ¹³C NMR spectroscopy (2, 3), ESI-MS and CID experiments (2, 3) as well as by ESR and magnetic measurements (μ_eff = 1.81, 298 K) for 4. Single X-ray diffraction analyses of 2 and 4 exhibited monomolecular complexes in which the titanium atom is distorted tetrahedrally coordinated by two η⁵-C₅Me₅ rings and by the chelating bound malonato-κ²O,O′ (2) and N,N-dimethylglycinato-κ²O,O′ ligand (4).