Tripodal Schiff Base Research Articles

Magnetic and spectroscopic properties of gadolinium tripodal Schiff base complex

Gadolinium(III) tripodal Schiff base (tris(((5-chlorosalicylidene)amino)ethyl)amine) complex has been obtained and investigated by infrared spectroscopy (IR), magnetic susceptibility, and electron paramagnetic resonance (EPR) methods. Comparison of IR bands in ligand and gadolinium complex confirmed the formation of the gadolinium complex and allowed to propose its structure. Both electron ionization and electron spray molecular spectroscopy spectra confirmed the [1:1] proportion of a ligand to metal in gadolinium tripodal Schiff base complex sample. IR spectroscopy and TG–DTA excluded the presence of water molecule in the metal coordination sphere. X-ray powder analysis applying Fullprof computer program has shown that the investigated sample was monophase with the monoclinic symmetry of the unit cell having the lattice constants: a = 10.028(4) Å, b = 13.282(5) Å, c = 21.20(1) Å and β = 101.58(4)°. Space group P21/ c, Z = 4. EPR spectra of the complex have been registered in the 4–300 K temperature range. Each spectrum has been fitted using EPR–NMR computer program and the values of the spin-Hamiltonian parameters at each temperature have been calculated. Temperature dependence of the integrated intensity of the EPR spectrum allowed revealing the magnetic interactions in the spin system of this compound. Comparison of the temperature dependence of dc magnetic susceptibility ( χ) and EPR susceptibility ( χ EPR) showed significant differences between these quantities due to the presence of short-lived clusters with a non-magnetic ground state.

Tris(μ-phenoxo) bridged Cd(II) polymer synthesised from a symmetrical tripodal ligand: A novel observation for heptadentate monocapped trigonal antiprismatic Schiff base complex

A novel one-dimensional cadmium(II) polymer [Cd2(L){HCON(CH3)2}N(CN)2]n (H3L=condensation product of tris(2-aminoethyl)amine and salicylaldehyde) has been achieved from a tripodal Schiff base tris[(2-salicylaldeneimino)ethyl]amine or ‘trensal’. The structure confirmed from single crystal X-ray diffraction analysis reveals that each of the tris(μ-phenoxo) bridged individual Cd(II) dimeric units is interlinked via μ-(1,5) end-to-end (EE) dicyanamide [N(CN)2]− ligand framing a wavy chain polymer, which is believed to be the first report of its kind in the literature.

Metal complexes of a new potentially heptadentate(N 7) tripodal Schiff base ligand. Synthesis, NMR studies and ab initio calculations

Tris(3-aminopropyl)amine, 2-pyridinecarboxaldehyde and a number of metal ions were used to prepare metal complexes of a new fully condensed potentially heptadentate(N 7) tripodal Schiff base ligand (L 333). The resulting complexes, [M(L 333)](ClO 4) 2 {M= Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II); L 333=[N(CH 2CH 2CH 2N CH(C 5H 4N)) 3]}, were characterized by microanalysis, IR and electronic spectra in all cases and by NMR spectra in the case of Zn(II) and Cd(II) complexes: these two are both seven-co-ordinate. The 1H NMR, COSY and HMQC spectra of these complexes show two kinds of protons for each methylene group. The COSY spectrum confirms the geminal coupling of the two protons of each methylene group, indicating that the protons are diastereotopic in rigid six-membered rings. In the 1H NMR spectrum of the cadmium complex the signal of the imine proton has two clear satellites peaks ( 3 J=41.9 Hz) with intensities in the ratio 1:6:1 due to coupling with neighbouring 111/113Cd. This coupling constant was confirmed by 113Cd NMR spectroscopy. Ab initio studies on [Fe(L 333)] 2+, [Zn(L 333)] 2+ and [Cd(L 333)] 2+ and also on the previously known complex, [Cd(L Me333)] 2+ are also reported. The results show that the shortest bonding interaction between the metal ion and the bridging tertiary nitrogen atom of the ligand is occurs in the Cd(II) complexes.

Synthesis of gadolinium(III) and samarium(III) complexes of new potentially heptadentate (N 4O 3) tripodal Schiff base ligands, and a theoretical study

Two new potentially heptadentate N 4O 3 Schiff base ligands {N[(CH 2) 3N CH(2-OH-3,5- t-Bu 2C 6H 2)] 3} (H 3L 1) and {N[(CH 2) 3N CH(2-OH-3,5- t-Bu 2C 6H 2)] 2 [(CH 2) 2–N CH(2-OH-3,5- t-Bu 2C 6H 2)]} (H 3L 2) were synthesized and characterized by various spectroscopic methods. The heptadentate N 4O 3 Schiff bases, H 3L 1 and H 3L 2, were derived from the condensation reaction of two tripodal tetraamine ligands, tris(3-aminopropyl)amine and (2-aminoethyl)-bis(3-aminopropyl)amine with 3 equiv. of 3,5-di- tert-butylsalicylaldehyde, respectively. The neutral gadolinium(III) and samarium(III) complexes, [Ln(L)], of these bulky ligands and also a gadolinium(III) complex of a previously known ligand, {N[CH 2CH 2N CH(2-OH-3,5- t-Bu 2C 6H 2)] 3} (H 3L 3), were also synthesized. All complexes were characterized by microanalysis, conductivity measurements, IR and UV–Vis spectra. The lanthanide atom is believed to be hepta-coordinate in the resulting complexes. The relative capability of H 3L 1, H 3L 2 and H 3L 3 as well as their unsubstituted analogs to encapsulate a lanthanide ion, herein La(III), has been theoretically studied by ab initio restricted Hartree–Fock (RHF) and density functional B3LYP methods.

Template Synthesis, Crystal Structure and Luminescent Properties of Neutral N4O3 Tripodal LnIIIL Complexes (LnIII = La3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+ or Lu3+; H3L = Tris{[3′‐(2′′‐pyridyl)‐5′‐tert‐butyl‐2′‐hydroxybenzylidene‐2‐imino]ethyl}amine)

AbstractIn the presence of Ln3+ (Ln = La, Eu, Gd, Tb, Dy, Ho, Er, Tm or Lu), tris(2‐aminoethyl)amine condensed with three equivalents of 3‐(2′‐pyridyl)‐5‐tert‐butyl‐2‐hydroxybenzaldehyde in methanol to give the neutral Schiff‐base complex LnIIIL (Ln = La 1, Eu 2, Gd 3, Tb 4, Dy 5, Ho 6, Er 7, Tm 8 and Lu 9; H3L = tris{[3′‐(2′′‐pyridyl)‐5′‐tert‐butyl‐2′‐hydroxybenzylidene‐2‐imino]ethyl}amine). The structures of compounds 4−7 were determined by X‐ray crystallography. The crystal structure analyses revealed that the Schiff base behaves as a tri‐deprotonated heptadentate ligand encapsulating the lanthanide metal ion within the N4O3 cavity, with all the pyridyl groups being pendant. Solution spectroscopic data suggest that the LnIIIL complexes remain intact in methanol and exist as nine‐coordinate non‐electrolytes with the lanthanide metal ions coordinated to the N4O3 cavity of the tripodal Schiff base and two solvent molecules. The solution photoluminescent properties of these lanthanide Schiff‐base complexes were also examined. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Neutral and ionic multiple hydrogen bonded moieties in crystal structure of a one tripodal Schiff base

Structural and spectroscopic properties of solid tris(3-formyl-5-methyl-2-salicylidenamino-ethyl)amine have been investigated. This is a compound containing two moieties with triple Schiff base fragments. One of the moieties has all three neutral intramolecular O–H⋯N hydrogen bonds, whereas there are only ionic H-bonds in the other moiety. Both moieties form cavities with the amine N atom lone electron pairs inside strongly shielded by three aliphatic wings. The H-bond formed in the Schiff fragments influence the other structural parameters of the nearest aromatic parts of the moieties. 13C and 15N CP/MAS NMR results (chemical shifts) allow to identify two pairs of Schiff and amino nitrogen nuclei thus supporting formation of the two types of moieties in the crystal lattice.

Novel copper(II) induced formation of a porphyrinogen derivative: X-ray structural, spectroscopic, and electrochemical studies of porphyrinogen complexes of Cu(II) and Co(III) complex of a trispyrazolyl tripodal ligand.

Copper(II) complexes of a novel pyrazole containing porphyrinogen and cobalt(III) and zinc(II) complexes of a pyrazole containing tripodal ligand having N-donor atoms have been investigated. 5-Methyl-3-formylpyrazole (MPA) on reaction with copper(II) nitrate or perchlorate in the presence of tris(2-aminoethyl)amine (tren) forms novel pyrazole-based porphyrinogen complexes [Cu(T(3)-porphyrinogen)(H(2)O)](NO(3))(2) (1a) and [Cu(T(3)-porphyrinogen)(H(2)O)](ClO(4))(2) (1b) where T(3)-porphyrinogen is 1,6,11,16-tetraaza-5,10,15,20-tetrahydroxy-2,7,12,17-tetramethylporphyrinogen. The same products are also obtained when tren is replaced by triethylamine. By contrast, the reaction between MPA, tren, and cobalt(II) perchlorate produces the cobalt(III) complex [Co(HMPz(3)tren)]ClO(4) (2) derived from the tripodal Schiff base tris[4-(3-(5-methyl-pyrazolyl)-3-aza-3-butenyl]amine (H(3)MPz(3)tren). The X-ray crystal structures of the copper(II) complexes (1a and 1b) and the cobalt(III) complex (2) have been determined. The structures show distorted square pyramidal coordination environments for 1a and 1b with the water molecule occupying the apical site, while for complex 2 a distorted octahedral geometry is obtained. Data for 1a follow: a = 19.476(3) A, b = 9.4116(8) A, c = 14.204(3) A; alpha = 90 degrees = gamma, beta = 107.58(2) degrees; V = 2482.0(7) A(3), Z = 4. Data for 1b follow: a = 20.967(3) A, b = 9.1563(18) A, c = 14.858(4) A; alpha = 90 degrees = gamma, beta = 108.44(3) degrees; V = 2706.0(10) A(3), Z = 4. Data for 2 follow: a = 21.293(3) A, b = 12.724(2) A, c = 19.777(4) A; alpha = 90 degrees = gamma, beta = 93.03(2) degrees; V = 5350.6(15) A(3), Z = 8. All three complexes crystallize in the monoclinic crystal system with the C2/c space group. The complexes are further characterized by UV-vis, IR, EPR, and electrochemical studies.

Synthesis, structure, spectra and redox behavior of a ruthenium(III) complex with a tripodal Schiff base ligand

The reaction of equimolar proportion of septadentate tripodal Schiff base ligand, tris[2-salicylidene(amino)ethyl]amine, II 3 L (1) and RuCl 3 .3H 2 O in refluxing methanol in presence of alkali has afforded a dark coloured compound of composition [Ru 1 1 1 L].CH 2 Cl 2 .H 2 O. X-Ray analysis of the complex shows that the septadentate ligand is coordinated octahedrally to ruthenium and tripodal nitrogen is nut in bonding distance (Ru....N(1) = 3.545(12) A) to ruthenium. The complex is redox-active and displays one one-electron reduction and one one-electron oxidation couples with E 1 / 2 values-0.58 and 0.61 V vs SCE, respectively.

Tripodal Iminophenolate Ligand Complexes of Gallium(III), Indium(III), and Thallium(III)

The polydentate tripodal Schiff base ligand H3L has been prepared by treating a methanolic solution of tris(aminoethyl)amine and 5-bromosalicylaldehyde. This ligand, and its complexes with group-13 metal ions (GaIII, InIII, and TlIII) have been characterized by elemental analysis, NMR spectroscopy, FAB+-MS, and X-ray diffraction analysis. The ligand, not preorganized in the solid state, acts as a hexadentate N3O3 ligand in all cases to form octahedral structures, the apical nitrogen not being involved in the chelation even for the [Tl(L)] complex. NMR studies reveal that the intact and rigid structures of the complexes are maintained in solution. For the [Tl(L)] complex, long-range thallium isotope effect on the chemical shift (δH and δC) and on the coupling constants (JTl-H and JTl-C) has been observed, confirming a strong and stable bond between TlIII and H3L.

Complexes of Indium (III) with Tripodal Schiff Base Ligands

The interaction of In (III) with tripodal Schiff base ligands (L 1-6) prepared from the condensation of substituted salicylaldehydes with tris(2-aminoethyl)amine gives a range of neutral complexes of the type [In (III) (L)] (salicylaldehyde L 1, θ-vanillin L 2, 5-methoxysalicylaldehyde L 3, 5-nitrosaliclaldehyde L 4, 3,5-di-i-butylsalicylaldehyde L 5, 5-bromosalicylaldehyde L 6). These complexes were investigated spectroscopically, and in two cases by single crystal X-ray diffraction, and are found to have heptacoordinate In (III) centres. In (III) (L 4) triclinic, P1 (#2), a = 11.766(3), b = 16.15(1), c = 9.283(5)A, α = 98.05(5), β = 102.76(3), γ = 100.23(4)°, Z = 2,5235 reflections, R = 0.114: In (III)(L s) triclinic, Pl (#2), a = 16.066(4), b = 23.293(3), c = 14.889(3)A, α = 103.38(1), β = 92.84(2), γ = 95.22(2), Z = 4, 16655 reflections, R = 0.072.

Hydrolysis, oxidation and complexation: the reactions of tin(II) chloride with a tripodal Schiff base ligand

The interaction of SnCl 2 · 2H 2O and the heptadentate tripodal Schiff base saltren yields in moderate yield the hexacoordinate Sn(IV) complex [Sn(saltren)]Cl (1). In addition, there is extensive destruction of the ligand, yielding the component triamine and aldehydes. The crystal structure of [Sn(saltren)]Cl · (salicylaldehyde) ( 1 · (sal)), is reported.

ChemInform Abstract: Some Copper(I) and Copper(II) Complexes of Two New Potentially Heptadentate Tripodal Schiff Base Ligands.

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Some copper(I) and copper(II) complexes of two new potentially heptadentate tripodal Schiff base ligands

Two potentially heptadentate tripodal Schiff base ligands, tris[4-(2-thienyl)-3-aza-3-butenyl]amine (S 3tren) and tris[4-(2-furyl)-3-aza-3-butenyl]