Matrix isolation vibrational spectra of alkyl chalcogenides complexed with HCl: Structure of alkyl sulfide and alkyl selenide complexes with hydrochloric acid in ar matrices from infrared spectra

The matrix isolation technique has been used to isolate the hydrogen-bonded complexes of hydrochloric acid with some methyl and ethyl sulfides and selenides. In the ir spectra the perturbed vibrational mode of the complexed acid was observed as a rather complicated, broad band which exhibits multiplet structure. Evidence was obtained for the coexistence of 1:1, 2:1 and 1:2 complexes. The shifts Δν_ClH… of the 1:1 complexes correlate with the proton affinity values of the chalcogenide bases. Isotopic dilution experiments using DCl allowed us to determine a bifide structure for the 1:2 R₂X · (HCl)₂ complexes.     

Spectroscopic Characterization of Complexes Obtained by Mechanochemical Reactions of Hemin

The solid state reactions of hemin with potassium acetate, KSCN, and Ag₂SO₄ were monitored using IR, Mössbauer and XRD techniques. These salts do not react at the peripheral propionic acid groups of hemin but form high spin complexes with hemin at the iron site. These complexes can be considered as ionic where the anions are coordinated to the metal through electrostatic interactions.     

Prediction of complexes of uranyl and organic substances by molecular orbital calculation

Structure of UO₂ ²⁺ complexes with salicylic acid was optimized by using molecular orbital calculation (ab initio method). The bond distances between U and O atoms (O_eq) of carboxyl group and phenyl group in salicylic acid were evaluated and compared with those measured experimentally by Denecke et al [1]. The calculated distance relatively agrees with the experimental one. The frontier electron densities in the complexes were also calculated. Strong localization of frontier electron density in the complexes was not observed, suggesting that the complexes are subject to only weak interactions with rocks, minerals and other compounds in the geosphere.     

Induced assembly and photoluminescence of lanthanum (Tb, Eu, Dy) complexes/ZnO/polyethylene glycol hybrid phosphors

Some novel kinds of hybrid phosphors were assembled with lanthanum (Tb, Eu, Dy) complexes (with four kinds of terbium complexes is 2,4-dihydroxybenzonic acid (DHBA), 1,10-phenanthroline (phen), acetylacetone (AA) and nicotinic acid (Nic), respectively) doped ZnO/PEG particles by co-precipitation approach derived from Zn(CH₃COO)₂ (Zn(AC)₂), NaOH, PEG as precursors at room temperature. The characteristic luminescence spectra for f-f transitions of Tb³⁺, Eu³⁺, Dy³⁺ were observed. It is worthy to point out that ZnO is the excellent host for lanthanum ions by the assembly of PEG matrices.     

Synthesis,spectroscopic, thermal and electrical conductivity studies of three charge transfer complexes formed between 1,3-di[(<Emphasis Type="Italic">E</Emphasis>)-1-(2-hydroxyphenyl)methylideneamino]-2-propanol Schiff base and different acceptors

Charge-transfer complexes (CTC) resulting from interactions of 1,3-di[(E)-1-(2-hydroxyphenyl) methylideneamino]-2-propanol Schiff base with some acceptors such as iodine (I₂), bromine (Br2), and picric acid (PiA) have been isolated in the solid state in a chloroform solvent at room temperature. Based on elemental analysis, UV-Vis, infrared, and ¹H NMR spectra, and thermogravimetric analysis (TG/DTG) of the solid CTC, [(Schiff)(I₂)] (1), [(Schiff)(Br₂)] complexes with a ratio of 1:1 and [(Schiff)(PiA)₃] complexes with 1:3 have been prepared. In the picric acid complex, infrared and ¹H NMR spectroscopic data indicate that the charge-transfer interaction is associated with a hydrogen bonding, whereas the iodine and bromine complexes were interpreted in terms of the formation of dative ion pairs [Schiff⁺, I₂^∙−] and [Schiff⁺, Br₂^∙−], respectively. Kinetic parameters were obtained for each stage of thermal degradation of the CT complexes using Coats–Redfern and Horowitz–Metzger methods. DC electrical properties as a function of temperature of these charge transfer complexes have been studied.     

Spectroscopic studies of electronic structure of copper(II) ethanolamine complexes in solutions and in impregnated wood

Optical and electron paramagnetic resonance (EPR) spectra were recorded for a series of Cu(II) complexes with monoethanolamine (EA) and the quaternary ammonium compound (QAC) alkyldimethylbenzylammonium chloride in aqueous solution with H₃BO₃ which are tested as modern impregnating solutions for wood preservation. It is proved that in aqueous solutions of Cu-EA the octahedral complexes I, Cu(EA)₂(H₂O)₂, exist with water in apical positions. The addition of the QAC results in an exchange of water for nitrogen of the QAC molecules with a possible partial destruction of the coordinating molecule (complex II). The detailed electronic structure is determined for both species I and II. Boric acid does not influence the complex structures. In the treated wood (Pinus silvestris L.) the complex I is destroyed and Cu(EA)₂ is attached to the OH groups of cellulose molecules, forming a stable complex. The complexes II still exist in wood, but with higher-concentration impregnating solution a part of these complexes is destroyed by coordination to the OH groups of cellulose molecules.     

Matrix isolation vibrational spectra of alkyl chalcogenides complexed with HCl: Matrix isolation IR spectra as a guide for the analysis of solution IR spectra of alkyl sulfide and alkyl selenide complexes with HCl

The ν_ClH… band in the solution IR spectra of alkyl sulfide and alkyl selenide complexes with HCl appears as a broad band which exhibits concentration-dependent subbands. Comparison with matrix isolation spectra allows one to assign these features to complexes with 1:1 and 1:2 stoichiometry. Perturbation of the bonded acid molecules is stronger in low-temperature inert matrices, but this strengthening seems to be dependent on the type of H bond.     

Photoactive thin films of polycaprolactam doped with europium (III) complex using phenylalanine as ligand

A photoactive complex based on europium(III) using the amino acid phenylalanine as ligand was prepared and characterized. The obtained europium(III)/phenylalanine complex presents an effective energy transfer from ligands to the rare earth center. The observed photoluminescent behavior for europium(III)/phenylalanine complex was similar to the well known europium(III)/ acetyl-β-acetonate hydrate. New photoactive polyamide thin films were prepared using polycaprolactam as host of these complexes. The structural characterizations of the films were studied through Rutherford backscattering (RBS), Fourier transform infrared (FTIR) and Raman spectroscopies. The polyamide films doped with the amino acid and acetyl-β-acetonate rare earth complexes maintain the original photoluminescent behavior, narrow emission bands corresponding to transitions ⁵D₀ → ⁷F_0-4, which indicates that this polymer is an excellent host to these complexes.     

Spectroscopic studies of the lanthanide(III) ions with pyridine carboxylic acid N-oxide ligands and in mixed ligand complexes

A series of Ln(III) complexes with pyridine carboxylic acid-N-oxides (L) Ln-L, and mixed ligand complexes of Ln-L plus bipyridine (bipy) or 1,10-phenanthroline (O-phen) (X) Ln-L-X have been studied. These complexes were characterized in solution using Nd(III) absorption in the spectral range of the ⁴I_9/2 → ⁴G_5/2 transition corresponding to the hypersensitive band, and in the solid state with the use of IR and Eu(III) luminescence spectroscopy. In solutions a series of Nd(III) complexes and mixed ligand complexes has been examined and the formation of binary LnL and LnL₂ complexes and mixed ligand LnL₂X complexes evidenced. Solid complexes of Eu(III) with nicotinic acid N-oxide and ternary with nicotinic acid N-oxide plus phen were studied with the use of Eu(III) luminescence lifetime measurements and IR spectroscopy, proving the formation of binary [Eu(nicN-oxide)₃(H₂O)₂].2H₂O and ternary [Eu(nicN-oxide)₃phen].H₂O complexes.     

Synthesis and Luminescence Properties of Two Novel Lanthanide (III) Perchlorate Complexes with Bis(benzoylmethyl) Sulfoxide and Benzoic Acid

Two novel ternary rare earth complexes of Tb(III) and Dy(III) perchlorates with bis(benzoylmethyl) sulfoxide (L) and benzoic acid (L′) had been synthesized and characterized by elemental analysis, coordination titration analysis, molar conductivity, IR, TG-DSC, ¹HNMR and UV spectra. The results indicated that the composition of these complexes was REL₅L′(ClO₄)₂·nH₂O (RE= Tb(III), Dy(III); L=C₆H₅COCH₂SOCH₂COC₆H₅, L′=C₆H₅COO; n = 6,8). The fluorescence spectra illustrated that the ternary rare earth complexes presented stronger fluorescence intensities, longer lifetimes and higher fluorescence quantum efficiencies than the binary rare earth complexes REL₅·(ClO₄)₃·2H₂O. After the introduction of the second ligand benzoic acid group, the relative fluorescence emission intensities and fluorescence lifetimes of the ternary complexes REL₅L′(ClO₄)₂·nH₂O (RE= Tb(III), Dy(III)) enhanced more obviously than the binary complexes. This indicated that the presence of both organic ligands bis(benzoylmethyl) sulfoxide and the second ligand benzoic acid could sensitize fluorescence intensities of rare earth ions, and the introduction of benzoic acid group was resulted in the enhancement of the fluorescence properties of the ternary rare earth complexes. The phosphorescence spectra were also discussed.     

Enhanced fluorescence of Tb(III), Dy(III) perchlorate by salicylic acid in bis(benzoylmethyl) sulfoxide complexes and luminescence mechanism

Two novel ternary rare earth perchlorate complexes had been synthesized by using bis(benzoylmethyl) sulfoxide as first ligand (L=C₆H₅COCH₂SOCH₂COC₆H₅), salicylic acid as second ligand (L^′=C₆H₄OHCOO⁻). The compounds were characterized by elemental analysis, TG-DSC and molar conductivities in DMF solution. The composition was suggested as [REL₅L′](ClO₄)₂·nH₂O (RE=Tb, Dy; n=6, 8 ). Based on IR, ¹HNMR and UV spectra, it showed that the first ligand, bis(benzoylmethyl) sulfoxide (L), bonded with Tb(III), Dy(III) ions by the oxygen atom of sulfinyl group. The second ligand, salicylic acid group (L′), not only bonded with RE(III) ions by one oxygen atom of carboxyl group but also bonded with RE(III) ions by oxygen atom of phenolic hydroxyl group. In bis(benzoylmethyl) sulfoxide system, fluorescent spectra of the complexes showed that the luminescence of Tb(III), Dy(III) ions was enhanced by the second ligand salicylic acid. The ternary complexes had stronger fluorescence than the binary ones where only bis(benzoylmethyl) sulfoxide acted as ligand. Phosphorescent spectra of the two ligands indicated that the coordination of salicylic acid resulted in the matching extent increasing between the triplet state of ligand and excited state of the rare earths. The relationship between fluorescence lifetime and fluorescence intensity was also discussed.     

Properties of cationic pnicogen-bonded complexes F4-nHnP+:N-base with H–P···N linear and n = 1–4

Ab initio MP2/aug'-cc-pVTZ calculations have been carried out to investigate the pnicogen-bonded complexes F_4-nH_nP⁺:N-base, for n = 1–4, each with a linear or nearly linear H_ax–P···N alignment. The sp³-hybridised nitrogen bases include NH₃, NClH₂, NFH₂, NCl₂H, NCl₃, NFCl₂, NF₂H, NF₂Cl, and NF_3, and the sp bases are NCNH₂, NCCH₃, NP, NCOH, NCCl, NCH, NCF, NCCN, and N₂. Binding energies increase as the P–N distance decreases, with an exponential curve showing this relationship when complexes with sp³ and sp hybridised bases are treated separately. However, the correlations are not as good as they are for the complexes F_4-nH_nP⁺:N-base for n = 0–3 with F–P···N linear. Different patterns are observed for the change in the binding energies of complexes with a particular base as the number of F atoms in the acid changes. Thus, the particular acid–base pair is a factor in determining the binding energies of these complexes.

Three different charge-transfer interactions stabilise these complexes, namely N_lp→σ*P–H_ax, N_lp→σ*P–F_eq, and N_lp→σ*P–H_eq. Unlike the corresponding complexes with F–P···N linear, N_lp→σ*P–H_ax is not always the dominant charge-transfer interaction, since N_lp→σ*P–F_eq is greater in some complexes. N_lp→σ*P–H_eq makes the smallest contribution to the total charge-transfer energy. The total charge-transfer energies of all complexes increase exponentially as the P–N distance decreases in a manner very similar to that observed for the series of complexes with F–P···N linear.

Equation-of-motion coupled cluster singles and doubles (EOM-CCSD) spin–spin coupling constants ^1pJ(P–N) across the pnicogen bond vary with the P–N distance, but different patterns are observed which depend on the nature of the acid, and for some acids, on the hybridisation of the nitrogen base. ^1pJ(P–N) values for complexes of F₃HP⁺ initially increase as the P–N distance decreases, reach a maximum, and then decrease with decreasing P–N distance as the P···N bond acquires increased covalent character. ^1pJ(P–N) for complexes with H–P···N linear and those with F–P···N linear exhibit similar distance dependencies depending on the number of F atoms in equatorial positions and the hybridisation of the base. Complexation may increase, decrease, or leave the P–H_ax distance unchanged, but ¹J(P–H_ax) always decreases relative to the corresponding isolated ion. Decreasing ¹J(P–H_ax) can be related to decreasing intermolecular P–N distance.     

Structure of complexes in the H<Subscript>2</Subscript>SO<Subscript>4</Subscript>—2-pyrrolidone system as determined by IR-spectroscopy and quantum-chemical calculations

Specific features of complexation in solutions of a strong dibasic acid in the H₂SO₄–2-pyrrolidone (Pyr) system (in the range of compositions of 0–100% H₂SO₄) are studied using multiple frustrated total internal reflection IR spectroscopy. The conclusions drawn on the structure of the complexes formed in such solutions are confirmed by quantum-chemical calculations of the mPyr · nH₂SO₄ (m, n = 1, 2) heteroassociates and by comparison of their calculated and measured vibrational spectra. It is found that, in the investigated solutions, four types of acid–base complexes, with various degrees of proton transfer in the OHO bridge, are formed: (AHA)^– anions with quasi-symmetric H-bonds, solvated by acid molecules, or entering into the composition of PyrH⁺ · (AHA)^– ion pairs; quasi-ion pairs with incomplete proton transfer to the base molecule of 1: 1 and 2: 2 compositions; and 2Pyr · H₂SO₄ complexes with two O–H···O bridges of molecular type. The main differences in the mechanisms of the acid–base interactions in the H₂SO₄–Pyr system as compared to the CH₃SO₃H–Pyr system result from the participation of two OH-groups of H₂SO₄ molecule in these interactions. Therefore, two types of quasi-ion pairs and complexes of 2Pyr · H₂SO₄ composition are formed.     

Tuning of carbon bonds by substituent effects: an ab initio study

ABSTRACT

An ab initio study, at the MP2/aug-cc-pVTZ level of theory, is performed to study σ-hole bond in binary XH₃C···CNY complexes, where X = CN, F, NO₂, CCH and Y = H, OH, NH₂, CH₃, C₂H₅, Li. This type of interaction is labelled as ‘carbon bond’, since a covalently bonded carbon atom acts as the Lewis acid in these systems. The geometrical and energetic parameters of the resulting complexes are analysed in details. The interaction energies of these complexes are between ?4.97 kJ/mol in (HCC)H₃C···CNH and ?23.07 kJ/mol in (O₂N)H₃C···CNLi. It is found that the electrostatic interaction plays a key role in the overall stabilisation of these carbon-bonded complexes. To deepen the understanding of the nature of the carbon-bonding, the molecular electrostatic potential, natural bond orbital, quantum theory of atoms in molecules and non-covalent interaction index analyses are also used. Our results indicate that the carbon bond is favoured over the C-H···C hydrogen bond in the all complexes considered and may suggest the possible important roles of the C···C interactions in the crystal growth and design.     

Luminescence properties of europium(III) compounds with quinaldic acid and nitrogen-containing ligands

Luminescent mixed-ligand Eu(III) complexes with quinaldic acid and nitrogen-containing dimeric ligands are synthesized. The thermal and spectral-luminescent properties of the obtained mixedligand Eu(III) complexes are studied. It is shown that a water molecule and a neutral ligand are detached during thermolysis in two stages with endothermic effects. It is found that the quinaldinate ion is coordinated to a europium(III) ion in a bidentate fashion. The Stark structure of the 5D₀–7F _j (j = 0, 1, 2) transitions in the low-temperature luminescence spectra of europium(III) complexes is analyzed.     

Lysozyme complexes with thermo- and pH-responsive PNIPAM-<Emphasis Type="Italic">b</Emphasis>-PAA block copolymer

Lysozyme is an enzyme responsible for the damage of bacterial cell walls and is abundant in a number of secretions such as tears and human milk. In the present study, we investigated the structure, the physicochemical characteristics, and the temperature-responsiveness of lysozyme complexes with poly(N-isopropylacrylamide)-b-poly(acrylic acid) block polyelectrolyte in aqueous media. A gamut of light-scattering techniques and fluorescence spectroscopy were used in order to examine the complexation process, as well as the structure, solution behavior, and temperature response of the nanosized complexes. The concentration of copolymer polyelectrolyte was kept constant. The values of the scattering intensity, I ₉₀, which is proportional to the mass of the species in solution, increased gradually as a function of C _LYS, providing proof of the occurring complexation, while the size of the nanostructures decreased. The structure of the complexes became more open as the C _LYS increased. The increase of the salinity did not affect the structural characteristics of the supramolecular nanoparticulate aggregates. On the other hand, the physicochemical and structural characteristics of the complexes changed upon increasing temperature, and the changes depended on the initial ratio block polyelectrolyte/lysozyme. The knowledge on developing block polyelectrolyte/protein complexes through electrostatic interactions, obtained from this investigation, may be applied to the design of nutraceuticals.     

DFT study of the effect of different metals on structures and electronic spectra of some organic-metal compounds as sensitizing dyes

Ruthenium polypyridined-derivative complexes are used in dye-sensitized solar cell [DSSC] as a light to current conversion sensitizer. In order to lower the cost of the DSSC the normal transition metals were used to replace the noble metal ruthenium, and some compounds [ML₂L′] (M = Pt, Fe, Ni, Zn; L = isonicotinic acid, L′ = maleonitriledithiolate, I = PtL₂L′, II = FeL₂L′, III = NiL₂L′, IV = ZnL₂L′) were selected as the replacement. The geometries, electronic structures and optical absorption spectra of these compounds have been studied by using density functional theory (DFT) calculation at the B3LYP/LANL2DZ, B3P86/LANL2DZ, B3LYP/GEN level of theory. All the geometric parameters are close to the experimental values. The HOMOs are mainly on the maleonitriledithiolate groups mixed with fewer characters of the metal atom, the LUMOs are mainly on the two pyridine ligands. This means that the electron transition is attributed to the LLCT. The maximum absorptions of complexes are found to be at 351 nm, 806 nm for compound I, and 542 nm for compound II. The maximum absorptions of complexes are found to be at 884 nm for compound III, and 560 nm for compound IV. This means that those compounds may be as a suitable sensitizer for solar energy conversion applications.     

Complexability of o-bisguanidinobenzenes with arsenic and phosphoric acids in solution and solid states, and the potential use of their immobilized derivatives as solid base ligands for metal salts and arsenic acid

The role of o-bisguanidinobenzenes (BGBs) as new Brønsted base ligands for arsenic and phosphoric acids was examined. In solution state, complexation was evaluated by Job’s plot in ¹H NMR experiment, indicating a 1:1 complex formation, whereas in solid state crystalline structures of complexes obtained were addressed by X-ray crystallographic analysis and/or solid state ¹³C NMR experiment, in which 1:2 complexes between the BGB and the acid components were normally formed. Based on these results, Merrifield and Hypogel^® resin-anchored BGBs were designed and prepared as the corresponding polymer-supported host ligands. Evaluation of their coordination ability with metal salts (ZnCl₂ and CoCl₂) and arsenic acid in aqueous media by ICP-MS showed that the latter Hypogel^® resin-anchored BGBs acted as effective immobilized base ligands.     

Regium bonds formed by MX (M═Cu,Ag, Au; X═F,Cl, Br) with phosphine-oxide/phosphinous acid: comparisons between oxygen-shared and phosphine-shared complexes

ABSTRACT

Regium bonds interaction between phosphine oxide (H₃PO), the trans phosphinuous acid (T-PH₂OH), the cis phosphinuous acid (C-PH₂OH) and MX (M═Cu, Ag, Au; X═F, Cl, Br) complexes were investigated by means of ab initio MP2/aug-cc-pVTZ method. For phosphinuous acid and MX complexes, two types of regium bonded interaction (trans and cis complexes) are observed and the two types of structures are very easily transformed from one type to another due to a low energy barrier. The molecular interaction energies are in the order of Au?>?Cu?>?Ag, F?>?Cl?>?Br and increase with the decrease of intermolecular distance R_int. Two resonance-type structures of P:M-X (ωI) ? P–M:X (ωII), O:M-X (ωI) ? O–M:X (ωII) are recognised by the natural resonance theory (NRT) and the natural bond orbitals (NBOs) analysis. The competition between ωI ? ωII resonance structures mainly arises from hyperconjugation interactions, in all phosphor-shared complexes, P–M:X resonance accounts for a larger proportion which leads to the covalent characters. All of complexes have been described in terms of their electron density properties.     

Infrared and Mössbauer Spectral Studies on Some Tin(IV) Complexes: A Qualitative Correlitation with the Hard and Soft Acid-Base Theory

The principle of the hard and soft acid-base theory (HSAB) is that binding of hard acids with hard bases and soft acids with soft bases is preferred.¹ This implies that the maximum bond strength in a series of acid-base complexes should occur, all other factors being equal, where the degree of hardness or softness of the acid and base are most nearly matched. To test this hypothesis, we prepared a number of tin(IV) complexes of varying softness with the soft base 2,5-dithiahexane (CH₃SCH₂CH₂OCH₃, DTH) and the hard base 1,2-dimethoxyethane (CH₃OCH₂CH₂OCH₃, DME). The acids employed were SnCl₄, CH₃,SnCl₃, SnBr₄, and SnI₄. The complexes thus obtained were studied by infrared and Mcssbauer techniques in order to determine which, if any, of the complexes exhibited spectral details which could be correlated with HSAB.