UV-vis Spectra Of Complexes Research Articles

Azobenzenyl Calcium Complex: Synthesis and Reactivity Studies of a Ca(I) Synthon.

Attempted preparation of a low-valent Ca(I) complex by reduction of Ca iodide precursor [LCaI(THF)]2 (1) (L = [CH3C(NAr)CHC(CH3)NCH2CH2N(CH3)2]-, Ar = 2,6-iPr2C6H3), with KC8 led to isolation of a dinuclear calcium azaallyl complex {[H2CC(NAr)CHC(CH3)(NCH2CH2N(CH3)2)]Ca(THF)}2 (2). Alternatively, reaction of 1 with KC8 in the presence of azobenzene gives an azobenzenyl calcium complex LCa(PhNNPh)(THF) (3). The electron paramagnetic resonance and UV-vis spectra of complex 3 suggest that the (PhNNPh) moiety should be regarded as a radical anion. Complex 3 can react with Me3SiN3, Me3SiCHN2, CS2, W(CO)6, elemental sulfur, and AgBr, resulting in the formation of the azido complex [LCaN3(THF)]2 (5), isonitril complex {LCa[CNN(Si(CH3)3)]}2 (6), dimeric bis(thiolate) complex {[S2CC(CMe(NAr))C(Me)NCH2CH2NMe2]Ca(DME)}2 (7), metallocyclic carbene complex {[OC(W(CO)5)N(C6H5)]Ca(THF)3}2 (8), bis(thiolate) complex {[S2C(CMe(NAr))C(Me)NCH2CH2NMe2]Ca(THF)}2 (9), and bromide complex [LCaBr(THF)]2 (10). Additional insights on the reaction process resulting in the formation of complex 7 are provided by density-functional theory studies. These results demonstrate that the (PhNNPh)•- radical anion can serve as a very potent one-electron donor, and 3 acts as a low-valent calcium(I) synthon.

Experimental and theoretical studies on cis-dioxomolybdenum(VI) complexes of ONN-donor thiosemicarbazone

Cis-dioxomolybdenum(VI) chelate complexes with 5-chloro-2-hydroxybenzophenone S-methyl-4-phenylthiose- micarbazone (L) were synthesized in the general formula (MoO$_{2}$(L)D), where D is an odd- or even-numbered alcohol (methanol (1), ethanol (2), n-propanol (3), n-butanol (4), and allyl alcohol (5)). The structures of 1-5 were verified by elemental analysis, Fourier transform infrared (FT-IR), and $^{1}$H NMR spectra. Complex 5 crystallizes in the monoclinic space group P21/n, and its crystalline data showed a dimeric structure formed by a pair of intermolecular hydrogen bonds with 1.92 Å. These dimers are stacked in a similar crystalline structure as a single molecule. The experimental data were compared with the theoretical results obtained by the quantum chemical calculations of the DFT/B3LYP method with LANL2DZ basis set. A detailed interpretation of the FT-IR spectra of the studied compounds was performed based on the total energy distribution. In order to investigate the electronic structures and the UV-Vis spectrum of complex 5, time-dependent density functional theory calculation was taken into account. The interaction energies between the odd- and even-numbered alcohols and remaining parts of complexes 1-4 were evaluated with the help of natural bonding orbital analysis. In addition, the basis set superposition error correction energies were calculated. The results were evaluated by considering the coordinated alcohols with an even number of carbon atoms to have much higher interaction energy than the next lower homologous alcohols with an odd number of carbon atoms.

Synthesis of biscyclometalated iridium(III) acetylacetonate complexes via a 15 min bridge-splitting reaction, their characterisations and photophysical properties

Chloro-bridged diiridium(III) complexes (4a and 4b) were subjected to a bridge-splitting reaction with acetylacetone and sodium carbonate in 2-ethoxyethanol. The reaction was complete within 15 min and two novel biscyclometalated iridium(III) acetylacetonate complexes (5a and 5b) were successfully obtained in 41% and 63%, respectively. Complexes (5a and 5b) were fully characterised by 1H, 13C NMR, FT-IR and elemental analysis. UV-Vis spectra of complexes (5a and 5b) showed two absorption bands: a strong one appears below 400 nm due to ligand-centered (LC, π-π*) transitions and the weak one arises between 400 and 600 nm due to metal-to-ligand charge-transfer (MLCT, d- π*) transitions. The emission of the complexes (5a and 5b) arises in the red region of the spectrum, emitting ca. 675 nm for 5a and ca. 625 nm for 5b. A short emission lifetime (62 ns) for complex 5a indicates emission originates from 3LC transitions. However longer emission lifetime (657 ns) for complex 5b confirms that the emission totally results from 3MLCT transitions.

Thiacalix[4]arene derivatives containing multiple aromatic groups: High efficient extractants for organic dyes

Click reaction of alkynylthiacalix[4]arene with ethyl 2-azidoacetate, followed by ammonolysis with hydrazine hydrate and Schiff-base condensation with benzaldehyde or salicyic aldehyde, afforded two novel thiacalix[4]arene derivatives containing multiple aromatic groups in yields of 86% and 90%. Their complexation properties for four organic dyes were investigated by liquid-liquid extraction experiments, complexation UV-Vis spectra and mass spectrum. The highest extraction percentage was 97% for Neutral red. The UV-Vis spectra and ESI-MS spectrum indicated the 1:1 complexes in DMSO solution. The association constants were as high as 1 ∼ 8×104 M−1. These complexation experiments showed that thiacalix[4]arene receptors possess excellent complexation capabilities for dyes. Two novel thiacalix[4]arene derivatives containing multiple aromatic groups were synthesized in yields of 86% and 90%. These complexation experiments showed that thiacalix[4]arene receptors possess excellent complexation capabilities for four tested dyes.

Synthesis, crystal structures and spectroscopic properties of cobalt(II) complexes with chelating sulfonylamidophosphate ligands

Two new cobalt(II) complexes with general formula Co(L1)2Phen (1) and Co(L2)2Phen (2), in which HL1 = dimethyl phenylsulfonylphosphoramidate and HL2 = dimethyl tosylphosphoramidate, were prepared in one-step synthesis and characterized by IR, UV-VIS spectroscopy, TGA-DTA and elemental analysis. Moreover, the single crystal structures of 1 and 2 were determined by single crystal X-ray diffractometry. Complexes consist of mononuclear units comprising two L1−(or L2−) and phenanthroline ligands bidentatly linked to metal ion. The UV-VIS spectra of complexes in the solid state show broad asymmetric band at 530 nm attributed to the d–d transition of the metal ion. Comparing of these spectra with the absorption spectra in acetone, octahedral environment of the cobalt(II) ion in solution were considered. The structural similarity of 1 and 2 leads to a similar thermal decomposition profile.

A series of lanthanide coordination polymers constructed from 4-pyridin-4-ylbenzoate

Four lanthanide coordination polymers, LaL3(H2O)2(1), LnL2(µ3-OH)(H2O)[Ln=Eu(2),Tb(3)] and ErL3·2H2O(4) were synthesized via hydrothermal reactions of lanthanide oxide with 4-pyridin-4-ylbenzonic acid(HL), and characterized by means of elemental analyses, infrared(IR) spectrometer, powder X-ray diffraction(PXRD), thermogravimetric analyses(TGA) and single-crystal XRD. The results reveal that complex 1 possesses a linear chain structure, complexes 2 and 3 possess isostructural ladder-like chains, while complex 4 possesses a 2D layer with 4-connected sql topology. Furthermore, the luminescence properties and UV-Vis spectra of complexes 2 and 3 were investigated.

Calix[4]benzocrown-[60]fullerene dyads: synthesis and complexation properties for dyes

Two novel calix[4]benzocrown-[60]fullerene dyads were obtained by refluxing calix[4]benzocrown derivative containing formacyl group with sarcosine or glycine and C60 in toluene at reflux via 1,3-dipolar cycloaddition of azomethine ylides tied to C60 in the yields of 30 and 28 %, respectively. Their structures and conformations were characterized by UV–Vis, 1H NMR, ESI–MS, elemental analysis. Their complexation properties for four dyes were studied by liquid–liquid extraction experiments, complexation UV–Vis spectroscopy and complexation ESI–MS spectroscopy. The results of liquid–liquid extraction suggested that they exhibited excellent extraction abilities towards the four test dyes with the extraction percentages fluctuating in the scope of 75–90 %. The complexation UV–Vis spectra showed the 1:1 complexes between hosts and guests in DMSO solution. The association constants were as high as 5.40 × 104–1.05 × 106 M−1. The formation of 1:1 complex was further confirmed by the complexation ESI–MS spectrum of compound 4a for Neutral red in DMSO solution. These complexation experiments implied that the novel calix[4]benzocrown-[60]fullerene dyads possess excellent complexation abilities for organic dyes.

Syntheses and dye-binding abilities of novel calix[4]benzocrowns with π-conjugate azo groups on sidechains

Three novel calix[4]benzocrowns with π-conjugate azo groups on sidechains were designed and synthesized in ideal yields. Their structures and conformations were characterized by IR, 1H NMR, ESI–MS, elemental analysis. Their complexation abilities for dyes were investigated by liquid–liquid extraction experiments, complexation UV–Vis spectra and complexation ESI–MS spectra. The complexation experimental results suggested that they possessed excellent extraction abilities towards dyes. The highest extraction percentage of compound 3a for neutral red was 89.5 %. The complexation UV–Vis spectra of compounds 3a–c with four dyes indicated the 1:1 complexes between host and guest in DMSO solution. The association constant of compound 3b with OI was as high as 3.93 × 106 M−1. The complexation ESI–MS spectrum of compound 3c for Neutral red also supported the 1:1 complexes of host and guest. The complexation experiments showed these novel calix[4]arene receptors possess excellent complexation capabilities for dyes.

Novel Calixarene Benzo-15-crown-5 Derivatives: Synthesis and Complexation for Dyes

Three novel calix[4]arene, thiacalix[4]arene and calix[6]arene crown ether derivatives 6, 7 and 8 with integral crown ether rings were designed and synthesized in ideal yields by multiple procedures. The liquid-liquid extraction experiment showed that they possessed excellent extraction abilities towards three cationic and one anionic dyes [Orange I (OI), Methylene blue (MB), Neutral red (NR), Brilliant green (BG)]. The highest extraction percentage of compound 8 for Neutral red was 88.2%. Their complexation UV-Vis spectra with four dyes indicated 1:1 complexes between host and guest in DMSO solution. The complexation results and IR spectra suggested the crown ether ring, the bridging functional groups, and the cavity of calixarene unit participated in the complexation for dyes. The larger calixarene cavity was favorable for binding dyes. The association constant of compound 8 with BG was as high as 6.4×105 M−1.

Novel 1,2-3,4-Bridged and 1,3-Bridged Calix[4]arene Based on Large s-triazine Conjugate Systems: Synthesis and Complexation for Dyes

Two novel 1,2-3,4-bridged and 1,3-bridged calix[4]arenes 6 and 9 based on large s-triazine conjugate systems were designed and synthesized in high yields. The liquid-liquid extraction experiment showed that they possessed excellent extraction abilities towards one cationic and three anionic dyes [Orange I (OI), Methylene blue (MB), Neutral red (NR), Brilliant green (BG)]. The highest extraction percentage of compound 9 was 91.2% for BG. The complexation UV-Vis spectra of compounds 6 and 9 with four dyes indicated the existence of complexation action between hosts and guests with 1:1 ratio of complexation in DMSO solution. The association constants suggested that the 1,2-3,4-bridging structure was more favorable for producing excellent complexation abilities than 1,3-bridging structure. The association constant of compound 9 with BG was as high as 4.5 × 106 M−1.

Synthesis and Complexation Abilities of Novel Multiple-Sites Calix[4]arene Receptors: Calix[4]arene Derivatives with Anthraquinone Groups on Lower Rims and Hydrazone Groups on Upper Rims

By formylation of 1,3-bisubstituted calix[4]arene anthraquinone derivative 1 in hexamethylenetetramine/trifluoroacetic acid system, the corresponding formylated gecalix[4]arene anthraquinone derivative 2 was synthesized in yield of 63%. By further reacting compound 2 with salicylic hydrazide, 2,4-dinitrophenyl hydrazine, nicotinyl hydrazine or phenyl thiosemicarhazide, novel calix[4]arene derivatives with anthraquinone and hydrazone groups 3a–3d were obtained in yields of 74–83%. The extracting experiments for series of metallic cations showed that compounds 3a–3d possessed high extracting abilities and extracting selectivity for tested cations. The complexation UV-Vis spectra for a series of anions indicated compounds 3a–3d exhibited the strong complexation abilities for tested anions. The 1H-NMR titration study showed that compound 3d possessed excellent complexation abilities for ion-pair of NaH2PO4 in 1:1 host-guest complex with the association constant of 4.6 × 104 M−1.

Novel deep-cavity calix[4]arene derivatives with large s-triazine conjugate systems: synthesis and complexation for dyes

Two novel deep-cavity calix[4]arenes 3 and 4 with large s-triazine π-conjugate systems were designed and synthesized in high yields by reacting calix[4]arene with mono phenyl-substituted cyanuric chloride or further substitution with aniline. The liquid–liquid extraction experiment showed that they possessed excellent extraction abilities towards one cationic and three anionic dyes (Orange I, methylene blue, neutral red, brilliant green). The highest extraction percentage of compound 4 was 88.8 % for brilliant green. The complexation UV–Vis spectra of compounds 3 and 4 with four dyes indicated the existences of complexation action between hosts and guests with 1:1 ratio of complexation in DMSO solution. The association constants suggested that the larger π-conjugate system of compound 4 possessed the stronger complexation abilities than that of compound 3. The association constant of compound 4 with BG was as high as 8.1 × 106 M−1.

A novel asymmetric di-Ni(ii) system as a highly efficient functional model for phosphodiesterase: synthesis, structures, physicochemical properties and catalytic kinetics

A novel asymmetric phenol-based 'end-off' dinucleating ligand 2-{[(2-piperidylmethyl)amino]methyl}-4-bromo-6-[(1-methylhomopiperazine-4-yl)methyl]phenol (HL) and three dinuclear nickel(II) complexes, [Ni₂L(μ-OH)] (ClO₄)₂ (1), [Ni₂L(DNBA)₂(CH₃CN)₂]BPh₄ (2) and [Ni₂L(BPP)₂(CH₃CN)₂]BPh₄ (3) have been synthesized and characterized by a variety of techniques including: NMR, infrared and UV-vis spectroscopies, mass spectrometry, elemental analysis, molar conductivity, thermal analysis, magnetochemistry and single-crystal X-ray diffractometry. The UV-vis spectrum of complex 1 exhibits a strong peak at 510 nm, a characteristic absorption of a d-d transition of the square-planar four-coordinated Ni(II) center. Utilizing this feature, the stepwise formation of mono- and dinickel centers in solution can be monitored. Phosphodiesterase activity of a dinuclear Ni(II) system (complex 1), formed in situ by a 2 : 1 mixture of Ni(2+) ions and the ligand HL, was investigated using bis(4-nitrophenyl)phosphate (BNPP) as the substrate. The pH dependence of the BNPP cleavage in water-ethanol (1 : 1, v/v) reveals a bell-shaped pH-k(obs) profile with an optimum at about pH 8.3 which is parallel to the formation of the dinuclear species [Ni₂L(μ-OH)](2+), according to the increase of the peak at 510 nm in the UV-vis absorption spectrum . These studies reveal that the di-Ni(II) system shows the highest catalytic activity reported so far, with an acceleration rate 1.28 × 10⁷ times faster than the uncatalyzed reaction. The bridging hydroxyl group in [Ni₂L(μ-OH)](2+) is responsible for the hydrolysis reaction. The possible mechanism for the BNPP cleavage promoted by di-Ni(II) system is proposed on the basis of kinetic and spectral analyses. This study provides a less common example of the asymmetric phosphodiesterase model, which is like the active sites of most native metallohydrolases.

Synthesis, characterisation and photochemistry of Pt(IV) pyridyl azido acetato complexes.

Pt(II) azido complexes [Pt(bpy)(N(3))(2)] (1), [Pt(phen)(N(3))(2)] (2) and trans-[Pt(N(3))(2)(py)(2)] (3) incorporating the bidentate diimine ligands 2,2'-bipyridine (bpy), 1,10-phenanthroline (phen) or the monodentate pyridine (py) respectively, have been synthesised from their chlorido precursors and characterised by X-ray crystallography; complex 3 shows significant deviation from square-planar geometry (N(3)-Pt-N(3) angle 146.7 degrees ) as a result of steric congestion at the Pt centre. The novel Pt(IV) complexes trans, cis-[Pt(bpy)(OAc)(2)(N(3))(2)] (), trans, cis-[Pt(phen)(OAc)(2)(N(3))(2)] (), trans, trans, trans-[Pt(OAc)(2)(N(3))(2)(py)(2)] (), were obtained from via oxidation with H(2)O(2) in acetic acid followed by reaction of the intermediate with acetic anhydride. Complexes 4-6 exhibit interesting structural and photochemical properties that were studied by X-ray, NMR and UV-vis spectroscopy and TD-DFT (time-dependent density functional theory). These Pt(IV) complexes exhibit greater absorption at longer wavelengths (epsilon = 9756 M(-1) cm(-1) at 315 nm for 4 ; epsilon = 796 M(-1) cm(-1) at 352 nm for 5 ; epsilon = 16900 M(-1) cm(-1) at 307 nm for 6 , in aqueous solution) than previously reported Pt(IV) azide complexes, due to the presence of aromatic amines, and 4-6 undergo photoactivation with both UVA (365 nm) and visible green light (514 nm). The UV-vis spectra of complexes 4-6 were calculated using TD-DFT; the nature of the transitions contributing to the UV-vis bands provide insight into the mechanism of production of the observed photoproducts. The UV-vis spectra of 1-3 were also simulated by computational methods and comparison between Pt(II) and Pt(IV) electronic and structural properties allowed further elucidation of the photochemistry of 4-6.

Syntheses, structures, and spectroscopic properties of copper(II) and cobalt(III) complexes containing 1,4,7-tribenzyl-1,4,7-triazacyclononane ligand

Three new complexes [CuL(N3)2] (1), [CuL(SCN)2] (2), and [CoL(SCN)3] (3) (L = 1,4,7-tribenzyl-1,4,7-triazacyclononane) have been synthesized and structurally characterized. Complex 1 crystallizes in monoclinic space group P2(1)/n with unit cell parameters a = 14.105(7), b = 8.999(5), c = 21.603(11) Å, β = 100.470(7)°. While 2 crystallizes in triclinic space group P-1 with unit cell parameters a = 9.6380(16), b = 10.6993(18), c = 15.798(3) Å, α = 106.636(3), γ = 116.478(3)°. Complex 3 crystallizes in trigonal space group P–3c1 with unit cell parameters a = 14.744(3), b = 14.744(3), c = 16.098(4) Å, γ = 120°. Elemental analysis, IR, UV-vis spectra of complexes 1–3 and ESR spectra of complexes 1–2 were also determined.