Spectroscopic characterization of charge-transfer complexes of morpholine with chloranilic and picric acids in organic media: Crystal structure of bis(morpholinium 2,4,6-trinitrocyclohexanolate)

Electron donor–acceptor interaction of morpholine (morp) with chloranilic acid (cla) and picric acid (pa) as π-acceptors was investigated spectrophotometrically and found to form stable charge-transfer (CT) complexes (n–π*) of [(Hmorp)₂(cla)] and [(Hmorp)(pa)]₂. The donor site involved in CT interaction is morpholine nitrogen. These complexes are easily synthesized from the reaction of morp with cla and pa within MeOH and CHCl₃ solvents, respectively. ¹HNMR, IR, elemental analyses, and UV–vis techniques characterize the two morpholinium charge-transfer complexes. Benesi–Hildebrand and its modification methods were applied to the determination of association constant (K), molar extinction coefficient (?). The X-ray crystal structure was carried out for the interpretation the predict structure of the [(Hmorp)(pa)]₂ complex.     

Preparation and spectroscopic studies on charge-transfer complexes of 2,2'-bipyridine with picric and chloranilic acids

Charge-transfer (CT) complexes formed on the reaction of 2,2'-bipyridine with some acceptors such as picric acid (HPA) and chloranilic acid (H(2)CA) have been studied in CHCl(3) and MeOH at room temperature. Based on elemental analysis and IR spectra of the solid CT complexes along with the photometric titration curves for the reactions, the data obtained indicate the formation of 1:1 charge-transfer complexes [(bpyH)(PA)] and [(bpyH(2))(CA)], respectively. The infrared and (1)H NMR spectroscopic data indicate a charge-transfer interaction associated with a proton migration from the acceptor to the donor followed by intramolecular hydrogen bonding. The formation constants (K(C)) for the complexes were shown to be dependent on the structure of the electron acceptors used.     

Synthesis and characterization of N,N'-bis[2-hydroxyethyl]-1,4,6,8-naphthalenediimide with para substituted of phenols based on charge-transfer complexes

The interaction of charge-transfer (CT) complexes resulted from the reaction of N,N'-bis[2-hydroxyethyl]-1,4,6,8-naphthalenediimide (BHENDI) with some various acceptors like as substituted phenols in para position; 4-aminophenol (4AP), 4-methylphenol (4MP) and 4-nitrophenol (4NP) have been studied in methanol at room temperature. The reaction was studied using electronic (UV-vis), mid infrared, and (1)H NMR spectra and thermal measurements (TGA and DTG) as well as elemental analysis CHN. The chemical analysis data of the resulted CT-complexes, BHENDI-acceptors, reveal that the formation of a 1:2 CT complexes in all cases. The interaction of N,N'-bis[2-hydroxyethyl]-1,4,6,8-naphthalenediimide and phenolic acceptors were investigated spectrophotometrically and found two detected CT bands have n-pi(*) transition. The donor site involved in CT interaction is the diimide two nitrogen atoms by forming hydrogen bonding. The kinetic thermodynamic parameters like DeltaE, DeltaH, DeltaS and DeltaG are calculated from the DTG diagrams using Coats-Redfern method. The electrical conductivity properties for the solid CT complexes were measured within the temperature of room 25 degrees C.     

Anion radical formation in the reaction of chloranilic acid with n-methylpiperidine in acetonitrile

Reaction of chloranilic acid with N-methylpiperidine in acetonitrile has been studied. The product of the reaction is an unusually stable anion radical of quinone. The presence of radicals has been confirmed by EPR measurements. Stability constant, extinction coefficients and thermodynamic reaction parameters are reported. Mechanism of the reaction is proposed. This revised version was published online in June 2006 with corrections to the Cover Date.     

水与氯冉酸的荷移反应及其分析应用

用分光光度法研究了氯冉酸与水的荷移反应, 探讨了反应机理, 确定了反应条件. 氯冉酸与水形成紫色络合物的最大吸收波长为530 nm. 水量在0.13%～6%范围内呈线性关系, 检出限为体积分数0.13%, 相对标准偏差小于2%. 用本法测定乙醇、面粉及香料中的微量水, 与标准方法测定值相符, 回收率为97%～102%.     

Intermolecular hydrogen bond complexes by in situ charge transfer complexation of o-tolidine with picric and chloranilic acids

A two new charge transfer complexes formed from the interactions between o-tolidine (o-TOL) and picric (PA) or chloranilic (CA) acids, with the compositions, [(o-TOL)(PA)(2)] and [(o-TOL)(CA)(2)] have been prepared. The (13)C NMR, (1)H NMR, (1)H-Cosy, and IR show that the charge-transfer chelation occurs via the formation of chain structures O-H?N intermolecular hydrogen bond between 2NH(2) groups of o-TOL molecule and OH group in each PA or CA units. Photometric titration measurements concerning the two reactions in methanol were performed and the measurements show that the donor-acceptor molar ratio was found to be 1:2 using the modified Benesi-Hildebrand equation. The spectroscopic data were discussed in terms of formation constant, molar extinction coefficient, oscillator strength, dipole moment, standard free energy, and ionization potential. Thermal behavior of both charge transfer complexes showed that the complexes were more stable than their parents. The thermodynamic parameters were estimated from the differential thermogravimetric curves. The results indicated that the formation of molecular charge transfer complexes is spontaneous and endothermic.     

Application of charge-transfer complexation for evaluation of the drug-receptor mechanism of interaction: Spectroscopic and structure morphological properties of procaine and pilocarpine complexes with chloranilic acid acceptor

Study of the charge-transfer or proton-transfer interaction of drugs is important for understanding the drug-receptor interactions and the mechanism of drug action. In the current research the corresponding data were accumulated in the course of synthesis and study of the H-bonded complexes originated from the interaction between procaine (Pro) or pilocarpine (Pil) drugs and chloranilic acid (CLA). The targeted microstructure products have been isolated and characterized by elemental and spectral (electronic and vibrational) data. Microstructural properties of the reported complexes were studied with XRD and SEM techniques. The Pil drug containing complex exhibited a specific electronic spectrum with a strong, broad absorption band with much longer wavelength, λ_max, than those typical for the individual reagents. It is noteworthy that the complex had good crystallinity. Application of Debye-Scherrer equation indicated that the reported complexes were in the range of nanosize.     

Infrared,Raman, 1H NMR,TG, and SEM properties of the charge-transfer interactions between tris(hydroxymethyl)methane with the acceptors picric acid,chloranilic acid,and 1,3-dinitrobenzene

Intermolecular charge-transfer complexes (CT) between the tris(hydroxymethyl)methane (THM) as a donor and picric acid (PA), chloranilic acid (CLA) and 1,3-dinitrobenzene (DNB) as a π-acceptor have been structurally, thermally and morphologically studied in methanol at room temperature. Based on elemental analyses (CHN), the stoichiometry of the obtained CT complexes (THM: acceptor molar ratios) was determined to be 1 : 1 for all three complexes. The CT complexes have been characterized via elemental analyses (CHN), IR, Raman and 1H NMR spectroscopy in order to predict the position of the CT interaction between the donating and accepting sites. Thermal decomposition behavior of these complexes was also investigated, and their kinetic thermodynamic parameters were calculated with Coats-Redfern and Horowitz-Metzger methods. Finally, the microstructure properties of these complexes were observed using scanning electron microscope (SEM).     

Synthesis,characterization, and structural determination of copper(II) complexes with alkyl derivatives of hydroxybenzophenones

Four mononuclear copper(II) complexes, [Cu(LFQM-115)₂] (1), [Cu(LFQM-116)₂] (2), [Cu(LFQM-117)₂] (3) and [Cu(octyloxy)₂] (4) [LFQM-115 = 2-hydroxy-4-O-methylbenzophenone (C₁₄H₁₁O₃), LFQM-116 = 2-hydroxy-4-O-butylbenzophenone (C₁₇H₁₈O₃), LFQM-117 = 2-hydroxy-4-O-(33-dimethylallyl)benzophenone (C₁₈H₁₈O₃) and octyloxy = 2-hydroxy-4-O-octylbenzophenone (C₂₁H₂₅O₃)], have been prepared and investigated by infrared spectroscopy, thermal analysis, and powder and single crystal X-ray diffraction. Even though the synthesis and infrared analysis of 1, 2, and 4 have been reported previously, their crystal structures were elucidated for the first time here. In addition, the crystal structures of LFQM-116 and LFQM-117 were also determined by single crystal X-ray diffraction. The pseudo-translational symmetry found in LFQM-116 and the isomorphism between LFQM-115 and LFQM-117 are discussed. The complexes were prepared from a reaction of copper(II) nitrate trihydrate and the respective ligand in a (1:2) molar ratio in methanol (for 1 and 2) or THF (for 3 and 4) with addition of NaOH. Furthermore, crystallographic studies show that each copper(II) exhibits a square planar geometry, coordinated by four oxygens of two ligands. The nature and crystal packing of the intermolecular interactions are discussed. Compounds 2 and 3 are isomorphic crystals and all structures have the same supramolecular synthon.     

Synthesis,characterization and interaction with DNA of mononuclear metal complexes with oxolinic acid

Seven new neutral mononuclear metal complexes of VO²⁺, Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺, Zn²⁺ and Cd²⁺ with the quinolone antibacterial agent oxolinic acid (=Hoxo) have been prepared and characterized with physicochemical and spectroscopic techniques. In all the complexes, oxolinic acid acts as a bidentate deprotonated ligand bound to the metal through the pyridone oxygen and one carboxylate oxygen. The metals in all the complexes are six-coordinate with slightly distorted octahedral geometry. The lowest energy model structures of the complexes Fe(oxo)₃, VO(oxo)₂(H₂O) and Mn(oxo)₂(H₂O)₂ have been determined with molecular modeling calculations. The ability of all the complexes to bind to calf-thymus DNA has been investigated with diverse spectroscopic techniques.     

Intermolecular charge-transfer complexes between chlorothiazide antihypertensive drug against iodine sigma and picric acid pi acceptors: DFT and molecular docking interaction study with Covid-19 protease

The interaction of chlorothiazide (CH) as donor (D) with picric acid (PA) and iodine (I₂) as π- and σ-acceptors (A), respectively, gives charge-transfer (CT) complexes as a final products. The reaction of donor and acceptors were studied spectrophotometrically. The complexes are generally of the n-π* and n-σ* types, with the ground state wave function primarily characterized by the non-bonding structure. For the micro determination of chlorothiazide using picric acid and iodine as acceptors, the ideal conditions encouraging the formation of complexes are thoroughly explored. It was discovered that the stoichiometry of the molecular structure is 1:1 (D:A). The equilibrium constant and the molar extinction coefficient were calculated using Benesi-Hildebrand and its modifications. DFT/TD-DFT calculations with B3LYP/LanL2DZ and 6-311G++ level of theory were used to provide comparable theoretical data along with electronic energy gap of HOMO→LUMO. Molecular docking calculations have been performed between CT complexes and Covid-19 protease (6LU7) to study the interaction between them and their inhibitory effect.     

Synthesis, characterization and antitumor properties of titanocene derivatives with thiophene containing ligands

The titanocene complexes [TiCp₂(Cl)R] (1), [TiCp₂(Cl)SR] (2), [TiCp₂(SR)₂] (3) with R = benzothienyl (BT) A and dibenzothienyl (DBT) B, were synthesized and the molecular structures of [TiCp₂(Cl)DBT] (1B) and [TiCp₂(Cl)SDBT] (2B) confirmed by single crystal X-ray diffraction studies. The dibenzothiophene rings are planar and for 1B in the plane of the titanium and chloro ligand. The chloro ligand is in a trans position to the sulfur atom with respect to the titanium-carbon bond. The complexes were studied for their electronic and structural features and preliminary tests were conducted for their tumor inhibiting properties against HeLa and COLO 320M tumor cell lines. These antitumor activities were compared against those observed for titanocene dichloride (S-01) under similar conditions and the highest antitumor activity was recorded for 2B.     

Spectroscopic study of the interaction of pazelliptine with nucleic acids

The antitumor drug pazelliptine (PZE) binds to natural and synthetic DNA sequences at 100 mM NaCl, pH 7.0, as deduced from the absorption and fluorescence data. Scatchard plots constructed from the results obtained with poly(dG-dC)-poly(dG-dC) give binding constants of base pairs in the range (2–6) × 10⁵ M⁻¹. The modifications in the absorption and fluorescence spectra observed when PZE binds to various polynucleotides, namely poly(dA-dT)-poly(dA-dT), poly(dA)-poly(dT), poly(dG-dC)-poly(dG-dC) and calf thymus DNA. reveal a change in the protonation state of the drug upon binding, increasing the apparent pK_a of its 9-N nitrogen atom. The PZE excited state properties serve as a sensitive probe to distinguish between homo and hetero A-T sites as well as between AT and GC sites. Fluorescence studies reveal that energy transfer occurs from polynucleotide bases to the bound PZE chromophore, a result consistent with an intercalative mode of binding of the drug to DNA. The emission is enhanced when PZE is bound to A-T base pairs ( 30% increase of φ_F) whereas it is quenched in the vicinity of G-C base pairs ( 90% decrease of φ_F). Furthermore, the fluorescence spectrum obtained with calf thymus DNA is hardly distinguishable from that obtained with poly(dG-dC)-polu(dG-dC), suggesting a binding of PZE to G-C rich regions.     

氧氟沙星荷移络合物的荧光特性和应用

研究了电子受体氯冉酸(CL)和2,3 二氰5,6 二氯1,4 对苯醌(DDQ)与电子给体氧氟沙星之间的荷移反应。实验发现,氧氟沙星与以上两种电子受体在氯仿中可生成稳定的n π络合物,其荧光强度较之氧氟沙星分别增强了22和54倍。据此建立了两种基于荷移反应简便可靠地测定氧氟沙星的荧光光谱新方法。CL法和DDQ法测定氧氟沙星的质量浓度分别为0 06～2.4μg/mL和0 16～2.0μg/mL时,荧光强度与质量浓度呈良好的线性关系。该方法已用于药物制剂中氧氟沙星的测定,其回收率分别为98.4%～100.9%和98.5%～100.4%。     

Synthesis, characterization, and X-ray structural analysis of some half-sandwich ruthenium(II) arene complexes with new N,S-donor Schiff base ligands

A series of cationic, half-sandwich ruthenium complexes with the general formula [(η⁶-arene)RuCl(R¹S-C₆H₄-2-CHNR²)]⁺ (arene = p-cymene or hexamethylbenzene; R¹ = CH₂Ph, ⁱPr, or Et; R² = aryl) have been prepared from the reaction of [(η⁶-arene)RuCl₂]₂ with various N,S-donor Schiff base ligands derived from 2-(alkylthio)benzaldehyde and several primary amines. All of the ruthenium complexes were characterized by IR, ¹H NMR, electrochemistry, and UV/Vis spectroscopies. The p-cymene complexes undergo irreversible oxidations while the hexamethylbenzene complexes undergo quasi-reversible oxidations. The molecular structures of ligand 1a and complexes 4a, 4l, and 5e were determined by X-ray crystallography.     

Synthesis and structural characterization of cationic octahedral oxorhenium(V) complexes with bidentate imidazole derivatives

Cationic distorted octahedral complexes [ReOCl(OEt)(L)(PPh₃)]X {L = 2-(1-ethylaminomethyl)-1-methylimidazole (eami), 2-(1-methylaminomethyl)-1-methylimidazole (mami), 2-(1-ethylthiomethyl)-1-methylimidazole (etmi); X=ReO₄, PF₆} were prepared by reaction of trans-[ReOCl₃(PPh₃)₂] with a twofold molar excess of L in ethanol under anaerobic conditions. X-ray structure determinations of [ReOCl(OEt)(eami)(PPh₃)](ReO₄) (1a) and its etmi equivalent (3a) were performed. In 1a coordination of the chloride occurs trans to the imidazole nitrogen. However, in 3a the chloride is coordinated trans to the ethereal sulfur donor of etmi.     

Synthesis,characterization, antimicrobial,SOD mimic and DNA interaction behavior of copper(II) complexes with pefloxacin and phenanthroline derivatives

Square pyramidal copper(II) complexes with second‐generation fluoroquinolone, pefloxacin and phenanthroline derivatives were prepared and characterized. They were also screened for in–vitro activity against two Gram^(+ve) and three Gram^(−ve) microorganisms. SOD mimic behavior was actively sought for clinical and mechanistic purposes under a nonenzymatic system (NBT–NADH–PMS), and was found to have good antioxidant activity. The complexes are avid DNA binders having binding constant (K_b) in the power of 4. Viscosity measurement data confirmed that complexes bind through classical intercalative mode of binding. The cleavage ability on pUC19 DNA was determined using gel electrophoresis technique. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis and structural peculiarities of gallium Complexes with novel paullone derivatives

9-Bromo-7,12-dihydroindolo[3,2-d][1]benzazepin-6-ylhydrazine was reacted with 2-acetylpyridine to give a Schiff base as a potential tridentate ligand. The reaction of this ligand with gallium chloride afforded complexes of 1:1 and 2:1 stoichiometry. The results of X-ray diffraction studies of the ligand and both gallium complexes are reported and compared with the data for a related gallium complex with a Schiff base obtained from 9-bromo-7,12-dihydroindolo[3,2-d][1]benzazepin-6-ylhydrazine and 2-hydroxybenzaldehyde.      

Synthesis and structural characterization of new mixed-ring indenyl derivatives of molybdenum containing phosphorus ligands

Reaction of NaBH₄ with [IndCpMo(dppe)](BF₄)₂ (1) in acetone yields [IndMo(η⁴-C₅H₆)(dppe)]BF₄ (2) quantitatively. The hydride addition takes place at the external face of the Cp ring. Dissolution of 2 in dichloromethane gives [IndMo(η⁴-C₅H₅-exo-CH₂Cl)(dppe)]BF₄, as confirmed by elemental analysis, IR and ¹H NMR spectroscopy. The similar dication [IndCpMo{P(OMe)₃}₂](BF₄)₂ (4) reacts with NaBH₄, in a solvent dependent manner. In acetonitrile, [IndMo(η⁴-C₅H₆){P(OMe)₃}₂]BF₄ (5) is obtained and in acetone a P(OMe)₃ ligand is lost resulting in the asymmetric phosphite-hydride, [IndCpMoH{P(OMe)₃}]⁺ (6). The molecular structures of [IndMo(η⁴-C₅H₆){P(OMe)₃}₂]PF₆ and [IndCpMoH{P(OMe)₃}]PF₆ were characterized by single-crystal X-ray diffraction.