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The synthesis of oxovanadium(IV) complex with 1-hydroxyethane-1,1-diphosphonic acid (H4EDP) anion and bis(2-pyridyl-1,2,4-triazol-3-yl)methane (H2L) is described. The reaction of VOSO4 with H4EDP and H2L followed by neutralization of the reaction mixture with Et3N gives the trinuclear complex [(VO)4(H2L)2(EDP)2(H2O)2]·4H2O (I), which was studied by IR and ESR spectroscopy. The molecular and crystal structures of complex I were determined by X-ray diffraction (CIF file CCDC no. 2022772).

Schiff bases have been synthesized by the reaction of triazole containing primary amine with aromatic carbonyl compounds. The Schiff bases prepared, act as ligand when these are made in contact with oxovanadium (VO2+) ion. Some new mononuclear oxovanadium(IV) complexes have been synthesized by the reaction of Schiff base ligands with vanadyl sulphate (VOSO4.xH2O) and the complexes are analyzed by different spectroscopic methods; [fourier-transform infrared (FTIR), ultraviolet-visible (UV-Vis.), electron paramagnetic resonance (EPR)], X-ray diffraction (XRD) analysis, elemental analysis, and conductivity measurement. The complexes have been well characterized based on analytical data. The electrolytic nature of the complexes was determined based on the molar conductance values. The powder XRD pattern has been used to determine crystal size and type. The synthesized Schiff base ligands and oxovanadium(IV) complexes were found to be stable in air and moisture at room temperature. On the basis of the physicochemical data, the tentative geometry of the complexes has been proposed. Antibacterial sensitivity of the ligand and its metal complexes have been assayed in vitro against bacterial pathogens viz. growth inhibitory activity of ligands and complexes against pathogens has also been determined.

This work describes the synthesis and characterization of a novel N-(dehydroacetic acid)-glucosamine oxovanadium(IV) complex. Both the experimental and the theoretical chemistry were applied in a c...

Three new series, each of hemi-discoid oxovanadium(IV) and copper(II) complexes based on halogen-substituted ‘salphen’ type ligands; H2L = [N,N-Bis(4-n-alkoxysalicylidene)-4-fluoro/chloro/bromo-1,2...

The data on the synthesis and study of the crystal structure of compounds {[K2Mg2(VO)3(Bumal)6(H2O)15] · 2H2O}n (I) and {[Cd(VO)(Bumal)2(H2O)5] · H2O}n (II) are presented. According to X-ray diffraction, these compounds are formed by the anionic fragments [VO(Bumal)2(H2O)]2– with oxovanadium(IV) and two butylmalonate anions (H2Bumal is C5H10(COOH)2) coordinated via the chelate mode. In the crystals of compound I (CIF file CCDC no. 1911220), the [VO(Bumal)2(H2O)]2– anionic fragments are bound to each other by the K+ and Mg2+ cations into the 2D polymeic structure. In compound II (CIF file CCDC no. 1033008), these fragments are bound by the Cd2+ cations to form the 1D coordination polymer.

The synthesis of some oxovanadium (IV) complexes with bidentate ligands (new synthesized biologically active hydrazones) derived from 2-methyl-4-(N-cyanoethyl)-N-benzenesulphonyl-benzylidene-3-oxo-[N-(substituted-1-phenyl)propanamido] hydrazone were analyzed.The complexes prepared were of the type [VO.L2] (where L= different new synthesized hydrazones).The characterization of these newly synthesized hydrazones and their metal complexes were done by IR, 1H-NMR spectral studies and elemental analysis. The infrared data of these complexes revealed the bidentate nature of the ligands and coordination to imino nitrogen of the amido group and azomethinic-nitrogen atoms. The new products were synthesized and evaluated for anti-tuberculosis activity against Mycobacterium tuberculosis H37RVin L.J.medium. The biological screening data indicates that the metal chelates are more potent than the parent ligands.

Diabetes mellitus (DM) is chronic and metabolic disorder, which is mainly attributed by hyperglycemia. Vanadium salts and their oxo-complexes have been shown to possess insulin-mimetic and anti-diabetic activities in animal models and diabetic patients. The main goal of this study was to investigate the protective effect of oxovanadium(IV) complex based on thiosemicarbazone (VOL) [L: (N(1)-2,4-dihydroxybenzylidene-N-(4)-2-hydroxybenzylidene-S-methyl-isothiosemicarbazidato-oxovanadium(IV)] on glycoprotein components levels and oxidative lung injury of streptozotocin (STZ)-induced diabetic rats. Male Swiss albino rats were separated into four groups. Group I (

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Three unique mixed-valence polyoxofluorovanadate clusters have been synthesized through a facile preparation process. The structure of these clusters is controlled by the addition of organic ligands. Single-crystal X-ray diffraction revealed that the clusters have the formula (XyH2)4[VV10VIV4O14(μ-O)10(μ3-O)10(μ3-F)2F4] (1), (Xy = m-xylylenediamine), (pyH)4(H)2[VV10VIV2O12(μ-O)8(μ3-O)10(μ3-F)2(pic)2] (2) and (pyH)4(H)3(Na+)[VV7VIV2O9(μ-O)8(μ3-O)4(μ5-F)(pic)4]2 (3), (py = pyridine, pic− = picolinate), with 2 and 3 representing the first examples of polyoxofluorovanadate clusters coordinated to a chelating ligand. The electron paramagnetic resonance (EPR) spectroscopy of 1 revealed that the spins of the VIV centers are coupled to each other, in contrast to the isolated spins of the isostructural [VV12VIV2O16(μ-O)10(μ3-O)10(μ3-F)2(L)2]6−, where L: im = imidazole (4) py (5). The trigonal bipyramidal coordinated VV atoms of 1, 4 and 5 mimic the structure of the active site of the vanadium dependent peroxidases and 4 and 5 exhibit peroxidase like activity. 43 45 17595 17602

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Sulfa drug Schiff base complexes of oxovanadium are counted among highly significant molecular scaffolds of industrial and medicinal relevance. In order to present a theoretical validation of our e...

Six new mixed-ligand oxovanadium(IV) and manganese(II) complexes of the general composition [VO(dhaH)(L1H)(L2)] and [Mn(dhaH)(L1H)(L2)], where dhaH=dehydroacetic acid, L1H=β-ketoenolates vi...

The aroylhydrazone Schiff base ligand N′-(2-hydroxy-3-methoxybenzylidene)-2-methoxybenzohydrazide (H2L) reacts with VO(acac)2 and 1,10-phenanthroline (Phen) in methanol to give the complex [N′-(2-h...

The results on the synthesis and study of the crystal structures of compounds based on anionic fragments {VO(Cbdc)2}2– formed by oxovanadium(IV) (vanadyl, VO2+) and two chelate-bound anions of cyclobutane-1,1-dicarboxylic acid (H2Cbdc = C4H6(COOH)2) are presented. The use of ammonium cation NH4+ as a counterion in the synthesis leads to the formation of the mononuclear complex (NH4)2[VO(Сbdc)2(H2O)] · 2H2O (I). In the case of K+ cation, compound [K4(VO)2(Сbdc)4(H2O)4] n (II) with the 3D polymeric crystal structure is formed. The reaction of compound II with Mg(NO3)2 · 6H2O in an aqueous solution involves the partial substitution of K+ by Mg2+ cations to form 1D polymeric compound {[KMg0.5(VO)(Сbdc)2(H2O)6.5] · 3H2O} n (III), while a similar reaction of compound I does not afford the product of substitution of NH4+ by Mg2+ cations (CIF files CCDC 1551021–1551023 for compounds I–III, respectively).

Polysaccharides and vanadium compounds have been studied due to their antitumor potential. In this study, the cytotoxic effects of galactomannan preparations on HepG2 cells were investigated. Native galactomannan from S. amazonicum (SAGM) and its modified form (MSAGM) were complexed with oxovanadium resulting in SAGM:VO and MSAGM:VO, respectively. The complexation was confirmed by NMR, FTIR, and AAS. SAGM and MSAGM:VO (250μg/mL) after 72h decreased viability by 51% and 58%, respectively, while the inhibition of the HepG2 cell proliferation was of ∼27% and ∼46%, respectively. SAGM and MSAGM:VO (250μg/mL) significantly inhibited all states of respiration (basal: 85% and 63%; uncoupled: 90% and 70%; and leak: 30% and 58%) after 72h. ROS levels increased by ∼149% after the treatment with MSAGM:VO (250μg/mL) for 72h, while ΔΨm decreased by ∼50%. Our results indicate that galactomannan preparations from S. amazonicum, especially SAGM and the MSAGM:VO complex, could be considered as potential antitumor drugs for further investigations, once they have the ability to make HepG2 cells susceptible to death by affecting vital cellular processes such as respiration and ROS generation.

A range of oxobis(phenyl-1,3-butanedione) vanadium(IV) complexes have been successfully synthesized from cheap starting materials and a simple and solvent-free one-pot dry-melt reaction. This direct, straightforward, fast and alternative approach to inorganic synthesis has the potential for a wide range of applications. Analytical studies confirm their successful synthesis, purity and solid-state coordination, and we report the use of such complexes as potential drug candidates for the treatment of cancer. After a 24 hour incubation of A549 lung carcinoma cells with the compounds, they reveal cytotoxicity values elevenfold greater than cisplatin and remain non-toxic towards normal cell types. Additionally, the complexes are stable over a range of physiological pH values and show the potential for interactions with bovine serum albumin.

Thin films of oxovanadium(IV) tetraphenylporphyrin (VOTPP) were prepared on quartz substrates by using thermal evaporation technique. The surface morphology and x-ray diffraction analysis of the VOTPP thin films were investigated. The micrographs of atomic force microscope of the films reveled nanostructure formation. The spectroscopic measurements of the transmittance and reflectance for VOTPP films were recorded in the spectrum range 190 –2000 nm, and from which many optical constants such as refractive index, extinction index and dielectric constant were determined. The absorption spectrum of VOTPP film showed an intense Soret band, two electronic quasi-states (Q-band) and two other bands (N and L) extended over the UV–Vis spectral region. The type of electronic transition bands of VOTPP films showed indirect allowed. The values of optical energies band-gaps were determined to be 1.89, 2.15 and 2.61 eV, in addition to Urbach tail energy was 0.044 eV. Furthermore, Wemple-DiDomenico model was applied to a normal dispersion region of the refractive index spectrum in order to extract many dispersion parameters such single oscillator energy, dispersion energy, infinite dielectric constant and lattice dielectric constant. The present spectroscopic results reveals that the thin films of VOTPP could be utilized as promising absorbing layers in energy conversion devices.

This study describes the synthesis of poly (hydroquinone-oxovanadium (IV)) porous hollow microspheres (poly HQVHMs) and their implementation as new modifier for voltammetric sensing of phenol (Ph). Poly HQVHMs present interesting electrocatalytic activity toward eletrooxidation of Ph in phosphate buffer solution (0.1 M, pH 2) to a well-defined oxidation peak at 0.88 V (vs. Ag/AgCl). The modified carbon paste electrode with poly HQVHMs (CPE/poly HQVHMs) displays a low detection limit of 30 nM and good linearity in the range of 0.5–150 µM. The applicability of CPE/poly HQVHMs for real sample analysis was further confirmed by the obtained recoveries in the range of 95.3 to 102.0%. Moreover, the results obtained by applying the proposed method were statistically compared with the results obtained by applying standard HPLC method. Calculated t-value showed no significant difference between our proposed method and standard HPLC method (t obtained = 0.34

We have investigated the properties as dyes of coordination compounds synthesized by us previously (8-(1',2'-naphthyl)-1-R-3-methyl-6-thiomethyl-4,5,7-triazanona-1,3,5,7-tetraenato-1,1'-diolato(-)-O1, O1', N4, N7-vanadil, where R=CH3 (1) , C6H5 (2)), which can be used for colouring thermoplastic masses. The compounds have a high photostability (7 points), thermostability (>250°) and an intensity of colour that give a low consumption (0.006-0.010g).

Oxovanadium(IV) compounds, [VO( O , O -R 1 COCHCOR 2 ) 2 ] (R 1 = R 2 = Me; R 1 = Me, R 2 = Ph; R 1 = R 2 = Ph), were established as a new class of environmentally friendly primary driers for solvent-borne alkyd binder. The performed experiments clearly show that the catalytic activity of oxovanadium compounds is, in some terms, considerably higher than observed for commercial cobalt-based drier ( Co-Nuodex ). The detailed study of the drying process reveals several differences in mechanism of autoxidation. The enhanced activity at low concentrations together with very low overall toxicity imply the oxovanadium compounds as promising catalysts of autoxidation reactions implying a great perspective in paint-producing industry.

The cyclic voltammetric (CV) studies of five binary oxovanadium (IV) complexes [VO(diimine)2]2 + where diimine = 4,4′-Me2bipy A; 5,5′-Me2bipy B; dmp C; bathophen D; and bathocuproin E and seven mixed-ligand oxovanadium (IV) complexes of dipicolinic acid (DPA) with diimines, [VO(DPA)(diimine)] where diimine = bipy 1; 4,4′-Me2bipy 2; 5,5′-Me2bipy 3; phen,4; dmp 5; bathophen 6 and bathocuproin 7 were carried out in dimethyl sulfoxide (DMSO). The reduction of binary [VO(diimine)2]2 + complex (VO2 +/V3 +) involving bathophen was the easiest while that involving dmp was the most difficult. The electronic spectra of all these binary [VO(diimine)2]2 + complexes in DMSO solution showed a weak broad band in the region 833–736 nm which was assigned to d–d transitions. The mixed-ligand complex involving 5,5′-Me2bipy was the easiest oxidation and bathophen was the most difficult to oxidize amongst all these complexes in the given medium. The reduction was the easiest in mixed-ligand complex involving bathophen and the most difficult in the case of dmp. The UV–visible spectra of all mixed ligand complexes were also studied in respective medium.

Antibacterial activities can be improved using mixed ligands. Mixed ligands involved in this research are sodium sulfadiazine (Na-sfz) and dithiocarbamate (ai-dtc). One-pot synthesis was used to synthesize ligand of aniline dithiocarbamate (ai-dtc) and the corresponding coordination compounds of [VO(sfz)(ai-dtc)] and [Zn(sfz)(ai-dtc)]. Crystals of ai-dtc, which grew from the solution when refrigerated after five days, were diffracted with technique of single crystal x-ray crystallography to reveal the structure. Other characterization techniques involving physicochemical parameters, FT-IR, UV-Vis and NMR (1H NMR and 13C NMR) were carried out on ligands of ai-dtc, sfz and corresponding coordination compounds. Differences in results of FT-IR, UV-Vis and NMR between ligands and their respective metal ions confirmed the coordination. The in vitro antibacterial studies showed that the ligands (not the metal complexes) had modest activity against Gram negative bacteria: Staphylococcus aureus, whereas, the coordination compounds had modest activities against the Gram negative bacteria: Escherichia coli and Pseudomonas aeruginosa.

Complexation in systems containing vanadyl cations and organophosphonic acid complexone anions (POC, Pocj), such as 1-hydroxyethylidenediphosphonic acid (HEIDP, Heidp4−), nitrilotrimethylphosphonic acid (NTP, Ntp6−), and 2-phosphonobutane-1,2,4-tricarbocylic acid (PBTC, Pbtc5−), was studied by absorption spectroscopy and potentiometry. The molar and protonic compositions of the complexonates formed and the regions of their formation and existence were determined. The equilibrium constants of reactions and the stability constants of the complexonates were calculated. Experimental data were processed by the mathematical models that were able of evaluating the possibility of the existence of a wide spectrum of complex species in solution and to select the species sufficient to confirm experimental data.

Bis(acetylacetonato)oxovanadium(IV) was immobilized on a self-assembled 4-(pyridine-4′-amido)thiophenol modified gold electrode. The modified electrode showed excellent electrocatalytic activity towards water oxidation at neutral pH. The turnover frequency of the catalyst for water oxidation was 0.64 s−1 at an overpotential of ~284 mV (at J = 3.82 mA cm−2).

The interaction of vanadyl sulfate VOSO4·3H2O and dimethylmalonic (H2Me2mal = = C3H6(CO2H)2), butylmalonic (H2Bumal = C4H10(CO2H)2), and cyclobutane-1,1-dicarboxylic (H2cbdc = C4H6(CO2H)2) acids with Na2CO3 at pH ∼4 in aqueous solutions gives crystals of compounds [Na4(VO)2(Me2mal)4(H2O)] n (1), {[Na6(VO)3(Bumal)6(H2O)15]· ·3H2O} n (2), and [Na2(VO)(cbdc)2(H2cbdc)(H2O)3] n (3), whose structures were determined by X-ray diffraction analysis. The formation of 3D (for 1) and 2D (for 2 and 3) polymer networks occurs in crystals of the compounds. These networks are constructed of mononuclear bis-chelate dianionic fragments [VOL2]2− (L is the corresponding dicarboxylic acid dianion) linked by the Na atoms. The magnetic properties of the obtained compounds were studied. The solid samples and solutions of complexes 1–3 were characterized by ESR spectroscopy.

A novel route to synthesize ternary oxovanadium(IV) complexes containing straight chain carboxylic acids and Schiff bases has been investigated. Complexes with the general formula [VO(OOCR)(SB)] (R˭C13H27, C15H31, or C17H35 and HSB = Schiff bases) have been isolated and characterized. The complexes were characterized by elemental analyses, molecular weight determinations, cyclic voltammetry, and spectral studies. Powder XRD and TEM studies indicated the particles of these were lying in the nano-size range. These are novel hydrolytically stable, mixed-ligand complexes in which vanadium is having coordination number 5. A square pyramidal geometry around vanadium has been assigned in all the complexes.

Two new 1:1 adducts of VO(dedtc)2, two 1:1 and two 1:2 adducts of Cu(dedtc)2 (where dedtc = diethyldithiocarbamate) with n-propylamine and isopropylamine have been prepared. The resulting complexes have been characterized by elemental analysis, molar conductance, magnetic susceptibility, IR and UV-Vis spectral and TGA/DTA techniques. Analytical data reveals that VO(IV) complex forms only 1:1 adducts with the formula (VO(dedtc)2L) while Cu(II) complex forms both 1:1 and 1:2 adducts with 1:1 adducts having general formula Cu(dedtc)2. L and 1:2 adducts having general formula Cu(dedtc)2.L2 (L = n-propylamine and isopropylamine). Antifungal activity of some complexes has been carried out against the fungal strain Sclerotium rolfsii. Electronic and magnetic measurements indicate a square pyramidal geometry for the 1:1 adducts of Cu(II) complex and an octahedral geometry for the 1:1 adducts of VO(IV) complex and for the 1:2 adducts of Cu(II) complex.

The bis(hydroxamato)oxovanadium(IV) complexes of composition [VO(IAH)2)] (I), [VO(IBH)2)] (II) and [VO(ICH)2)] (III) (where IAH = indole-3-acetohydroxamate; (C9H8NCONHO−); IBH = indole-3-butyrohydroxamate; (C11H12NCONHO−); ICH = indole-2-carbohydroxamate; (C8H6NCONHO−)) synthesized form the reactions of VOSO4·5H2O with bi-molar amounts of potassium salts of the respective hydroxamic acids in methanol have been characterised by elemental analyses, magnetic moment measurements and IR spectral studies. The thermal behaviour of complexes has been studied by TG and DTA techniques. Thermograms indicated that all complexes decompose in two steps yielding [VO(IAH)], [VO(IBH)] and [VO(ICH)] as intermediate of respective complexes and VO2 as the final product of decomposition in each case. From the initial decomposition temperatures (IDT), the order of thermal stability for the complexes has been inferred as II > I > III.

Diabetes mellitus is one of the metabolic disorders resulting from excess production of reactive oxygen species (ROS) over the normal level and also due to dysfunction in the antioxidant defense mechanism, possibly both occurring simultaneously. Excess ROS are normally scavenged by antioxidants. Transition metal complexes exhibit such antioxidant property by scavenging the excess free radicals (one type of ROS) in such disorders. In this study, we report on synthesis, characterization, and in vitro study on antioxidant property of a few new ester-based vanadium(IV) complexes, namely, bis(1,1-dimethylethylpropanedioato)oxovanadium(IV)—[VO(DTBM)2]; bis(methyl-3-oxopentanoato)oxovanadium(IV)—[VO(MPA)2]; bis(ethyl-3-oxopentanoato)oxovanadium(IV)—[VO(EPA)2]; bis(2-methyl-1,3-dimethylpropanedioato)oxovanadium(IV)—[VO(DMMM)2] and bis(2-bromo-1,3-diethylpropanedioato)oxovanadium(IV)—[VO(BDEM)2], and also furan-based vanadium complexes. Antidiabetic potential of selected complexes has been estimated. An attempt has also been made to correlate antioxidant and antidiabetic potentials of selected complexes. Our study reveals that compounds exhibiting higher glucose lowering effect seem to possess good antioxidant potential as well.

The thermal decomposition behaviours of oxovanadium(IV)hydroxamate complexes of composition [VO(Q)2−n(HL1,2)n]: [VO(C9H6ON)(C6H4(OH)(CO)NHO)] (I), [VO(C6H4(OH)(CO)NHO)2] (II), [VO(C9H6ON)(C6H4(OH)(5-Cl)(CO)NHO)] (III), and [VO(C6H4(OH)(5-Cl)(CO)NHO)2] (IV) (where Q = C9H6NO− 8-hydroxyquinolinate ion; HL1 = [C6H4(OH)CONHO]− salicylhydroxamate ion; HL2 = [C6H3(OH)(5-Cl)CONHO]− 5-chlorosalicylhydroxamate ion; n = 1 and 2), which are synthesised by the reactions of [VO(Q)2] with predetermined molar ratios of potassium salicylhydroxamate and potassium 5-chlorosalicylhydroxamate in THF + MeOH solvent medium, have been studied by TG and DTA techniques. Thermograms indicate that complexes (I) and (III) undergo single-step decomposition, while complexes (II) and (IV) decompose in two steps to yield VO(HL1,2) as the likely intermediate and VO2 as the ultimate product of decomposition. The formation of VO2 has been authenticated by IR and XRD studies. From the initial decomposition temperatures, the order of thermal stabilities for the complexes has been inferred as III > I > II > IV.

The reactions of oxovanadium(iv) salts with dimethylmalonate anions (H2Dmm — C3H6(COOH)2) and chelating N-donor ligands (2,2′:6′,2″-terpyridine (terpy), 2,2′-bipyridine (bpy)) led to the formation of new mononuclear heterochelate complexes [VO(Dmm)(terpy)]·4H2O (1) and [VO(Dmm)(bpy)(H2O)] (2). The structures of the synthesized compounds were determined by X-ray diffraction. The ESR spectra of the compounds at 293 and 100 K were analyzed and simulated. The photoluminescence properties were investigated.

We prepared [meso-tetrakis(4-carboxylatophenyl)porphyrinato]oxovanadium(IV) tetrasodium, ([VO(tcpp)]Na4), and investigated its in vitro insulin-mimetic activity and in vivo metallokinetic feature in healthy rats. The results were compared with those of previously proposed insulin-mimetic oxovanadium(IV)porphyrin complexes and oxovanadium(IV) sulphate. The in vitro insulin-mimetic activity and bioavailability of [VO(tcpp)]Na4 were considerably better than those of [meso-tetrakis (1-methylpyridinium-4-yl)porphyrinato]oxovanadium(IV)(4+) tetraperchlorate ([VO(tmpyp)](ClO4)4) and oxovanadium(IV) sulphate. On the other hand, [VO(tcpp)]Na4 and [meso-tetrakis(4-sulfonatophenyl) porphyrinato]oxidovanadate(IV)(4-)([VO(tpps)]) showed very similar in vitro insulin-mimetic activity and in vivo metallokinetic feature in healthy rats. In particular, the order of in vitro insulin-mimetic activity of the complexes was determined to be: [VO(tcpp)]Na4 ≈ [VO(tpps)] > ([VO(tmpyp)](ClO4)4 > oxovanadium(IV) sulphate.

The thermal decomposition behavior of oxovanadium(IV)hydroxamate complexes of composition [VO(acac)(C6H5C(O)NHO)] (I), [VO(C6H5C(O)NHO)2] (II), [VO(acac)(4-ClC6H4C(O)NHO)] (III), [VO(4-ClC6H4C(O)NHO)2] (IV) (where acac = (CH3COCHCOCH3 –) synthesized from the reactions of VO(acac)2 with equi- and bimolar amounts of potassium benzohydroxamate and potassium 4-chlorobenzohydroxamate in THF + MeOH solvent medium has been studied by TG and DTA techniques. TG curves indicated that complexes I, II, and IV undergo decomposition in single step to yield VO2 as the final residue, while complex III decomposes in two steps to yield VO(acac) as the likely intermediate and VO2 as the ultimate product of decomposition. The formation of VO2 has been authenticated by IR and XRD studies. From the initial decomposition temperatures, the order of thermal stability for the complexes has been inferred as IV > I > III > II.

The synthesis, liquid crystalline and optical properties of copper (II), oxovanadium (IV) and gadolinium (III) complexes derived from polar Schiff’s bases viz., N-(4-n-hexadecyloxysalicylidene)-4′-substituted anilines with methoxy, fluoro and chloro substituents in the 4-position of N-aryl moiety are presented. All the ligands exhibited smectic A phase except methoxy homolog which exhibited nematic phase. Majority of the complexes exhibited smectic A phase with some of them exhibiting smectic E phases. The UV–Visible and photo-luminescent properties of the ligands and complexes are also discussed.