N,N′-bis(2-hydroxy-3-methoxybenzylidene)-1,3-diaminopropane dimeric 4f and 3d-4f heterodinuclear complexes: Syntheses, crystal structures and magnetic properties

Three novel N,N′-bis(2-hydroxy-3-methoxybenzylidene)-1,3-diaminopropane dimeric lanthanide complexes, namely, [{H₂L}Sm(NO₃)₃]₂·H₂O (1), [{H₂L}Gd(NO₃)₃]₄·CH₃OH (2), [{H₂L}Lu(NO₃)₃]₄·H₂O (3) (H₂L = N,N′-bis(2-hydroxy-3-methoxybenzylidene)-1,3-diaminopropane) and three new N,N′-bis(2-hydroxy-3-methoxybenzylidene)-1,3-diaminopropane 3d-Gd heterodinuclear complexes, namely, [{LCo}(CH₃COO)(CH₃COOH)Gd(NO₃)₂] (4), [{LNi(MeOH)₂}Gd(NO₃)₃]·2MeOH (5) and [{(L)Zn(HNO₃)}Gd(NO₃)₃]·NO₃·H₃O·MeOH (6) have been synthesized and isolated. X-ray crystallographical analysis reveals that complexes 1-3 are isomorphic with unique dimeric topology. Complexes 4-6 are of discrete 3d-4f dinuclear cores. Magnetic properties of complexes 2 and 4-6 are systematically investigated. Complexes 4 and 5 are ferromagnetic, while 2 and 6 are antiferromagnetic.     

Syntheses, structures, and magnetic properties of 3d-4f heterometallic complexes constructed from pyrazole-bridged CuLn dinuclear units

A series of pyrazole-bridged heterometallic 3d-4f complexes, [CuDy(ipdc)₂(H₂O)₄] · (2H₂O)(H₃O⁺) (1) and [CuLn(pdc)(ipdc)(H₂O)₄] · H₃O⁺ (Ln = Ho (2), Er (3), Yb (4); H₃ipdc = 4-iodo-3,5-pyrazoledicarboxylic acid; H₃pdc = 3,5-pyrazoledicarboxylic acid), {[Cu₃Ln₄(ipdc)₆(H₂O)₁₆] · xH₂O}_n (Ln = Sm (5), x = 8.5; Ln = Eu (6), x = 7; Ln = Gd (7), Tb (8), x = 9), have been synthesized and structurally characterized. Ligand H₃ipdc was in situ obtained by iodination of ligand H₃pdc. Complexes 1-4 are pyrazole-bridged heterometallic dinuclear complexes, and 2-4 are isostructural. Complexes 5-8 are isostructural and comprised of an unusual infinite one-dimensional tape-like chain based on pyrazole-bridged heterometallic dinuclear units. The magnetic properties of compounds 1-4, 7 and 8 have been investigated through the magnetic measurement over the temperature range of 1.8-300 K.     

Synthesis, structures and luminescent properties of new heterobimetallic Zn-4f Schiff base complexes

A series of new 3d-4f heterobimetallic Schiff base complexes of the general formula [Zn(μ-L²)Ln(NO₃)₃(H₂O)_n] (Ln = La 1, Nd 2, Gd 3, Er 4 and Yb 5; n = 1 or 2; H₂L² = N,N′-bis(3-methoxy-5-p-tolylsalicylidene)ethylene-1,2-diamine) are synthesized and characterized. Complexes 1, 2, 4 and 5 are structurally characterized by X-ray crystallography. The photophysical properties of these complexes are also investigated. At room temperature, complexes 1-5 exhibit similar solution absorption and emission spectra in the UV-Vis region. Furthermore, compounds 2, 4 and 5 exhibit solution emission corresponding to the lanthanide(III) ion in the near-infrared region at room temperature. The triplet state emission of the 3d-4f bimetallic complexes without energy transfer is also determined through the photophysical study of complex 3.     

Extended molecular networks based on Zn and Cd imparting N-substituted imidazole

Synthesis of complexes with the formulations [M(CPI)₂Cl₂] (M = Zn, 1; M = Cd, 4) and [M(CPI)₆](X)₂ (M = Zn, X = NO₃⁻, 2; X = ClO₄⁻, 3; M = Cd, X = NO₃⁻, 5; X = ClO₄⁻, 6) have been achieved from the reactions of MCl₂, M(NO₃)₂·xH₂O and M(ClO₄)₂·xH₂O (M = Zn, Cd) with 1-(4-cyanophenyl)-imidazole (CPI). Complexes 1-6 have been characterized by elemental analyses and spectral studies (IR, ¹H, ¹³C NMR, electronic absorption and emission). Molecular structures of 1, 2, 3 and 6 have been determined crystallographically. Weak interaction studies on the complexes revealed presence of various interesting motifs resulting from C-H···N, C-H···Cl and π-π stacking interactions. The complexes under study exhibit strong luminescence at ∼450 nm in DMSO at room temperature.     

Synthesis, characterization, and magnetic properties of new homotrinuclear bis(oxamato) copper(II) complexes with an asymmetric central N,N′-bridge

The new mononuclear bis(oxamato) complex [n-Bu₄N]₂[Cu(obbo)] (1) (obbo=o-benzyl-bis(oxamato)) has been synthesized as a precursor for trinuclear oxamato-bridged transition metal complexes. Starting from 1 the homotrinuclear complexes [Cu₃(obbo)(pmdta)₂(NO₃)](NO₃)·CH₂Cl₂·H₂O (2) and [Cu₃(obbo)(tmeda)₂(NO₃)₂(dmf)] (3) have been prepared, where pmdta = N,N,N′,N″,N″-pentamethyldiethylenetriamine, tmeda = N,N,N′,N′-tetramethylethylenediamine and dmf = dimethylformamide. The crystal structures of 1-3 were solved. The magnetic properties of 2 and 3 were studied by susceptibility measurements versus temperature. For the intramolecular J parameter values of −111 cm⁻¹ (2) and −363 cm⁻¹ (3) were obtained.     

Synthesis, spectroscopic properties, X-ray single crystal analysis and antimicrobial activities of organotin(IV) 4-(4-methoxyphenyl)piperazine-1-carbodithioates

A series of mononuclear organotin(IV) complexes of the types, R₃SnL {R = C₄H₉ (1), C₆H₁₁ (2), CH₃ (3) and C₆H₅ (4)}, R₂SnClL {R = C₄H₉ (5), C₂H₅ (7) and CH₃ (9)} and R₂SnL₂ {R = C₄H₉ (6), C₂H₅ (8) and CH₃ (10)}, have been synthesized, where L = 4-(4-methoxyphenyl)piperazine-1-carbodithioate. The ligand-salt and the complexes have been characterized by Raman, FT-IR and multinuclear NMR (¹H, ¹³C and ¹¹⁹Sn) spectroscopy and elemental microanalysis (CHNS). The spectroscopic data substantiate coordination of the ligands to the organotin moieties. The structures of complexes 4 and 6 have been determined by single-crystal X-ray diffraction and illustrate the asymmetric bidentate bonding of the ligand. The packing diagrams indicate O···H and π···H intermolecular interactions in complex 4 and intermolecular S₂C···H interactions in complex 6, resulting in layer structures for both complexes. A subsequent antimicrobial study indicates that the compounds are active biologically and may well be the basis for a new class of fungicides.     

Synthesis, crystal structures and magnetic characterization of heterodinuclear CuGd and CuTb Schiff base complexes

Preparation, crystal structures and magnetic properties of new heterodinuclear Cu^IIGd^III (1) and Cu^IITb^III (2) complexes [CuLn(L)(NO₃)₂(H₂O)₃MeOH]NO₃·MeOH (where Ln = Gd, Tb) with the hexadentate Schiff-base compartmental ligand N,N′-bis(5-bromo-3-methoxysalicylidene)propylene-1,3-diamine (H₂L = C₁₉H₂₀N₂O₄Br₂) (0) have been described. Crystal structure analysis of 1 and 2 revealed that they are isostructural and form discrete dinuclear units with dihedral angle between the O1Cu1O2 and O1Gd1/Tb1O2 planes equal to 2.5(1)° and 2.6(1)°, respectively. The variable-temperature and variable-field magnetic measurements indicate that the metal centers in 1 and 2 are ferromagnetically coupled (J = 7.89 cm⁻¹ for 1). Crystal and molecular structure of the Schiff base ligand (0) has been also reported. The complex formation changes the conformation of Schiff base ligand molecule.     

Three-dimensional 3d-4f heterometallic polymers containing both azide and carboxylate as co-ligands

The hydrothermal reaction of Ln(NO₃)₃, Ni(NO₃)₂, NaN₃, and isonicotinic acid (L) yielded two novel 3-D coordination frameworks (1 and 2) of general formula [Ni₂Ln(L)₅(N₃)₂ (H₂O)₃] · 2H₂O (Ln = Pr(III) for 1 and Nd(III) for 2), containing Ni-Pr or Ni-Nd hybrid extended three-dimensional networks containing both azido and carboxylate as co-ligands. Both the compounds are found to be isostructural and crystallize in monoclinic system having P2₁/n space group. Here the lanthanide ions are found to be nonacoordinated. Both bidentate and monodentate modes of binding of the carboxylate with the lanthanides have been observed in the above complexes. Variable temperature magnetic studies of the above two complexes have been investigated in the temperature range 2-300 K which showed dominant antiferromagnetic interaction in both the cases and these experimental results are analyzed with the theoretical models.     

Structural studies of lanthanide complexes with tetradentate nitrogen ligands

Complexes have been synthesised with bis(2-pyridine carboxaldehyde) ethylenediimine (1) and bis(2-pyridine carboxaldehyde)propylene-1,3-diimine (2) with all of the available lanthanide trinitrates. Crystal structures were obtained for all but one complex with 1 and for all but one complex with 2. Four distinct structural types were established for 1 but only two for 2, although in all cases the structures contained one ligand bound to the metal in a tetradentate fashion. With 1, the four different structures of the lanthanide(III) nitrate complexes included 11-coordinate [Ln(1)(NO₃)₃(H₂O)] for Ln = La; 10 coordinate [Ln(1)(NO₃)₃(H₂O)] with one monodentate and two bidentate nitrates for Ln = Ce, then 10-coordinate [Ln(1)(NO₃)₃] for Ln = Pr-Yb with three bidentate nitrates; and 9-coordinate [Ln(1)(NO₃)₃] with one monodentate and two bidentate nitrates for Ln = Lu. On the other hand for 2 only two distinct types of structure are obtained, the first type with Ln = La-Pr and the second type for Ln = Sm-Lu, although all are 10-coordinate with stoichiometry [Ln(2)(NO₃)₃]. The difference between the two types is in the disposition of the ligand relative to the nitrates. With the larger lanthanides La-Pr the ligand is found on one side of the coordination sphere with the three nitrate anions on the other. In these structures, the ligand is folded such that the angle between the two pyridine rings approaches 90°, while with the smaller lanthanides Sm-Lu, two nitrates are found on one side of the ligand and one nitrate on the other and the ligand is in an extended conformation such that the two pyridine rings are close to being coplanar. In both series of structures, the Ln-N and Ln-O bond lengths were consistent with the lanthanide contraction though there are significant variations between ostensibly equivalent bonds which are indicative of intramolecular hydrogen bonding and steric crowding in the complexes.     

Synthesis and structural characterization of five-, six-, and seven-coordinate mononuclear manganese(II) complexes with N-tridentate ligands

A series of four mononuclear manganese (II) complexes with the N-tridentate neutral ligands 2,2^′:6,2^′′-terpyridine (terpy) and N,N-bis(2-pyridylmethyl)ethylamine (bpea) have been synthesized and crystallographically characterized. The complexes have five- to seven-coordinate manganese(II) ions depending on the additional ligands used. The [Mn(bpea)(Br)₂] complex (1) has a five-coordinated manganese atom with a bipyramidal trigonal geometry, while [Mn(terpy)₂](I)₂ (2) is hexa-coordinated with a distorted octahedral geometry. Otherwise, the reactions of Mn(NO₃)₂ · 4H₂O with terpy or bpea afforded novel seven-coordinate complexes [Mn(terpy)(NO₃)₂(H₂O)] (3) and [Mn(bpea)(NO₃)₂] (4), respectively. 3 has a coordination polyhedron best described as a distorted pentagonal bipyramid geometry with one nitrate acting as a bidentate chelating ligand and the other nitrate as a monodentate one. 4 possesses a highly distorted polyhedron geometry with two bidentate chelating nitrate ligands. These complexes represent unusual examples of structurally characterized complexes with a coordination number seven for the Mn(II) ion and join a small family of nitrate complexes.     

Syntheses, structures and fluorescence of lanthanide complexes of 4-acyl pyrazolone derivatives

Three lanthanide complexes of 4-acyl pyrazolone derivatives: Ln(PMPP-SHZ)₂(CH₃OH)₂ (Ln = Sm (1), Eu (2), Gd (3); PMPP-SHZ = N-(1-phenyl-3-methyl-4-propionyl-5-pyrazolone)-salicylidene hydrazide) have been synthesized and structurally characterized by X-ray crystallography. And all of them were carefully investigated by elemental analysis, thermal analysis and spectral characterization. The fluorescence of these three complexes 1-3 in solid state was investigated at room temperature. All complexes emit a blue emission band, and there are three characteristic emission peaks of Sm³⁺ evidently and one characteristic emission peak of Eu³⁺.     

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.     

Syntheses and characterization of 3D heterometallic (3d-4f) metal-organic frameworks: Reversible de- and rehydration performance and magnetic properties

By the “metalloligand” strategy, two new 3d-4f heterometallic metal-organic frameworks (MOFs), {[Ln₂Cu₃(IDA)₆] · 1.5H₂O}_n [Ln = Tb (1) and Dy (2); H₂IDA = iminodiacetate acid], had been prepared. X-ray crystal structure analyses show that 1 and 2 possess of 3D frameworks with highly ordered 1D channels along the c axis. The highly stable skeleton and reversible de- and rehydration performance of 1 are demonstrated by thermogravimetric and powder X-ray diffraction analyses, and a low temperature magnetic study of 2 reveals a weak ferromagnetic interaction between the metal ions.     

Syntheses, structures and properties of copper(II) complexes containing N-(2-hydroxybenzyl)-amino amide ligands

Four copper(II) complexes containing the reduced Schiff base ligands, namely, N-(2-hydroxybenzyl)-glycinamide (Hsglym) and N-(2-hydroxybenzyl)-l-alaninamide (Hsalam) have been synthesized and characterized. The crystal structures of [Cu₂(sglym)₂Cl₂] (1), [Cu₂(salam)₂(NO₃)₂] · H₂O (3), [Cu₂(salam)₂(NO₃)(H₂O)](NO₃) · 1.5H₂O (4), [Cu₂(salam)₂](ClO₄)₂ · 2H₂O (5) show that the Cu(II) atoms are bridged by two phenolato oxygen atoms in the dimers. The sglym ligand bonded to Cu(II) in facial manner while salam ligand prefers to bind to Cu(II) in meridonal geometry. Variable temperature magnetic studies of 3 showed it is antiferromagnetic. These Cu(II) complexes and [Cu₂(sglym)₂(NO₃)₂] (2), exhibit very small catecholase activity as compared to the corresponding complexes containing acid functional groups.     

Nature of the Ln-Co magnetic interactions in compounds [Ln2Co3(C5H4NPO3)6] · 4H2O with open-framework structures

The reactions of Ln(NO₃)₃ · xH₂O, CoSO₄ · 7H₂O or ZnSO₄ · 6H₂O and 2-pyridylphosphonic acid under hydrothermal conditions result in heterometallic phosphonate compounds with formula [Ln₂M₃(C₅H₄NPO₃)₆] · 4H₂O (Ln₂M₃; M = Co^II or Zn^II; Ln = La^III, Ce^III, Pr^III, Nd^III, Sm^III, Eu^III, Gd^III, Tb^III, Dy^III). These compounds are isostructural and crystallize in a chiral cubic space group I2₁3. Each structure contains the {LnO₉} polyhedra and {MN₂O₄} octahedra which are connected by edge-sharing to form an inorganic open-framework structure with a 3-connected 10-gon (10, 3) topology. The nature of Ln^III-Co^II magnetic interactions in Ln₂Co₃ is investigated by a comparison with their Ln^III-Zn^II analogues. It is found that the Ln^III-Co^II interaction is weak antiferromagnetic for Ln = Ce and ferromagnetic for Ln = Sm, Gd, Tb and Dy. In the cases of Ln = Pr, Nd and Eu, no significant magnetic interaction is observed.     

New supramolecular complexes generated from Mn, Fe, Co, Zn, Fe with a bent dipyridyl ligand: Metal- and anion-directed assembly

Assemblies of an angular dipyridyl ligand 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (4-bpo) with a series of metal perchlorate afford five new supramolecular complexes with the general formula of [M(4-bpo)₂(H₂O)₄] · (4-bpo)₂ · (anion) · (solvent), in which M = Mn^II for 1, Fe^II for 2, Co^II for 3, Zn^II for 4, and Fe^III for 5. Although similar molecular structures and compositions are found for these mononuclear complexes, they display two types of supramolecular lattices. Complexes 1, 4 and 5 similarly crystallize in space group P2/n or P2/c. The complex cations, free 4-bpo and lattice water are linked to generate 2D layered frameworks with the aid of hydrogen bonding, and the counter anions are located within and between (also methanol in 5) these 2D arrays. However, complexes 2 and 3 are isostructural in space group . Two types of alternate 2D layers consisting of complex cations and free 4-bpo components, respectively, are observed with the anions and lattice water locating between them. These motifs are interlinked by complicated hydrogen-bonding to form a 3D intercalated network. Moreover, when Co(NO₃)₂ is used instead of Co(ClO₄)₂ in the assembly of 3, a 1D polymeric chain complex {[Co(4-bpo)(H₂O)₂(NO₃)₂](H₂O)₃}_n (6) is generated. These results indicate that the choice of metal ion and anion exerts a significant influence on governing the target complexes. A comparison of the structural features for all metal perchlorate complexes with 4-bpo is also briefly discussed.     

Synthesis, crystal structures and magnetic behavior of two 3D coordination polymers using N-(4/3-carboxyphenyl)iminodiacetic acids as bridging ligands

Research on structure and magnetic properties of polynuclear metal complexes to understand the structural and chemical factors governing the electronic exchange coupling mediated by multi-atom bridging ligands is of growing interest. Hydrothermal treatment of Ni(NO₃)₂·6H₂O with N-(4-carboxyphenyl)iminodiacetic acid [N-4(H₃CPIDA)] at 150 °C yielded a 3D coordination polymer of general formula [Ni₃{N-4(CPIDA)}₂(H₂O)₃]·6H₂O (1). An analogous network of general formula [Co₃{N-3(CPIDA)}₂(H₂O)₃]·3H₂O (2) was synthesized using N-(3-carboxyphenyl)iminodiacetic acid [N-3(H₃CPIDA)] in combination with Co(NO₃)₂·6H₂O under identical reaction condition. Both the complexes contain trinuclear secondary building unit, and crystallized in monoclinic system with space groups C2/c (1) and P2₁/c (2), respectively. Variable temperature magnetic characterization of these complexes in the temperature range of 2-300 K indicated the presence of overall ferromagnetic and antiferromagnetic behavior for 1 and 2, respectively. Density functional theory calculations (B3LYP functional) were performed for further insight on the trinuclear units to provide a qualitative theoretical interpretation on the overall magnetic behavior of the complexes 1 and 2.     

Synthesis, characterization and l-lactide polymerization behavior of bis(amidinate) rare earth metal amide complexes

A family of neutral and solvent-free bis(amidinate) rare earth metal amide complexes with a general formula [RC(N-2,6-Me₂C₆H₃)₂]₂LnN(SiMe₃)₂ (R = phenyl (Ph), Ln = Y (1), Nd (2); R = cyclohexyl (Cy), Ln = Y (3), Nd (4)) were synthesized in high yields by one-pot salt metathesis reaction of anhydrous LnCl₃, amidinate lithium salt [RC(N-2,6-Me₂C₆H₃)₂]Li, and NaN(SiMe₃)₂ in THF at room temperature. Single crystal structural determination of complexes 1, 2 and 4 revealed that the central metal adopts distorted pyramidal geometry. In the presence of 1 equivalent of ⁱPr-OH, all these complexes were active for l-lactide polymerization in toluene at 70 °C to give high molecular weight (M_n > 10⁴) polymers.     

Calix[4]arene supported group 5 imido complexes

The reaction of imidoyl chlorides [V(NR)Cl₃] (R = Ph 1, Tol 2, tBu 3) and calix[4]arene methyl ether H₃Mecalix unexpectedly leads to the formation of the structurally characterized vanadium (IV) complex [VCl(Mecalix)] (4). Calix[4]arene methyl ether stabilized imido complexes of the type [V(NR)(Mecalix)] (R = Ph 7, Tol 8, tBu 9) were afforded from the reaction of [V(NR)Cl₃] (R = Ph 1, Tol 2, tBu 3) and the tris(lithium) or tris(sodium) salt of the calix[4]arene ether. The lithium salt [{Li₃(Mecalix)}₂] (5) is a dimer in the solid state, in which two monomeric trianions are bridged by lithium cations. Imido complexes [M(NR)(Mecalix)] (M = Nb: R = tBu, 12, R = Tol 13, R = Mes 14, R = Dipp 15; M = Ta: R = tBu 16, R = Tol 17) (Tol = 4-C₆H₄Me, Mes = 2,6-C₆H₃Me₂; Dipp = 2,6-C₆H₃iPr₂) have been prepared from structurally characterized [NbCl₂(Mecalix)] (10) and previously known [TaCl₂(Mecalix)] (11) via reaction with two equivalents of the appropriately metallated (Li, K) primary amine. The molecular structures of 13 and 15 confirm the mononuclear nature of these complexes.     

A series of pyrazolone lanthanide (III) complexes: Synthesis, crystal structures and fluorescence

A series of pyrazolone lanthanide complexes: Ln(PMPP)₃ · 2H₂O · C₂H₅OH (Ln = Nd (1), Sm (2), Gd (3), Dy (4); PMPP = 1-phenyl-3-methyl-4-propionyl-5-pyrazolone) have been synthesized by the hydrothermal method with the starting ligand PMPP-SAH (1-phenyl-3-methyl-4-(salicylidene hydrazone)-propionyl-5-pyrazolone) changed into PMPP during the formation process of complexes. All the complexes were structurally characterized by X-ray crystallography. The fluorescence of these four complexes 1-4 in solid state and DMF solution was investigated via F-4500 spectrophotometer and all of them indicate a fluorescent behavior at room temperature.