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• Stable inclusion complexes are formed between gliclazide and β-cyclodextrin in aqueous solutions. • The inclusion process was spontaneous and enthalpy driven. • The complexes were stabilized by hydrogen bonds between CO—HO and SO—HO groups and van der Waals contacts. • Gliclazide-β-cyclodextrin complexes can be considered as potential carriers for targeted drug transport and delivery. Gliclazide (GLC) inclusion complexes with β-cyclodextrin (βCD) were studied by UV–VIS and FT-IR spectroscopy. The recorded spectra confirmed formation of GLC-βCD binary complexes and GLC-(βCD) 2 ternary complexes in aqueous solutions. UV–VIS measurements carried out for a number of temperatures allowed to determine the binding constants of the complexation reactions. The bioavailability of GLC-βCD and GLC-(βCD) 2 was determined using the n-octanol/water partition coefficient. Experimental studies were supplemented with theoretical calculations. Quantum-chemical calculations and classical molecular dynamics simulations were used to describe the interactions in the host-guest inclusion complexes. [Display omitted] [ABSTRACT FROM AUTHOR]

• Two 1-D, 2-D and 3-D supramolecular Cu(II) and Ni(II) complexes based on the quinazoline-type ligand L containing pyrazole ring were structural characterized. • The activity data showed the metal complexes to be more antibacterial than the quinazoline-type ligand L. • The experimental investigations match with those obtained from TD-DFT calculations. • ESP calculation results confirmed the charge distribution in the molecule and Hirshfeld surface analyses of both complexes were also discussed. The ligand 2-(3-pyrazolyl)-4-methyl-1,2-dihydroquinazoline-N3-oxide (L) was synthesized, and two transition metal complexes, namely [Cu(L) 2 ]·(NO 3) 2 (1) and [Ni(L) 3 ]·(NO 3) 2 ·3CH 3 OH (2) were prepared through complexation reaction between L and the corresponding metal salt. L and both complexes were characterized by elemental analysis, as well as compared with spectrographic technique for example FT-IR and UV–Vis spectroscopy. X-ray single-crystal diffraction demonstrated that 1 was tetra-coordinated square planar whereas 2 was hexa-coordinated slightly distorted octahedral geometry. Meanwhile, the metal-ligand ratios were 2:1 in 1 whereas 3:1 in 2. Through the superposition of hydrogen bonds and other weak interactions, both complexes formed 1-D chain-like, 2-D layered, and 3-D supramolecular structures. Theoretical investigations explained the optimized geometries of complexes and the electrostatic potential distribution in molecules, and also analyzed the electron transition types of L and both complexes in combination with UV–vis spectroscopy, which provided theoretical support for the experimental conclusions. Electrostatic potential (ESP) was computed for both complexes to predict the reaction positions of electrophilic and nucleophilic assaults. Hirshfeld Surface Analysis quantified interactions in molecules and analyzed the contribution of various weak interactions to stabilize the structure of complexes. Especially, antibacterial experiments displayed compounds had certain antibacterial activities against both Gram-positive and Gram-negative bacterial strains. The ligand 2-(3-pyrazolyl)-4-methyl-1,2-dihydroquinazoline-N3-oxide (L) was synthesized, and two metal complexes, namely [Cu(L) 2 ]·(NO 3) 2 (1) and [Ni(L) 3 ]·(NO 3) 2 ·3CH 3 OH (2) were prepared through complexation reaction between L and the corresponding metal salt. Both complexes were characterized by X-ray crystallography, spectroscopic methods such as FT-IR and UV–Vis spectroscopy, and electrochemical property, as well as Hirshfeld surface analysis and DFT studies. The antimicrobial activities of all compounds were also compared. [Display omitted] [ABSTRACT FROM AUTHOR]

• influence of the substitution decoration in ferrocenyl selenophen-2-yl thioketone and ferrocenyl furan-2-yl thioketone utilized as a proligand in complexation reactions with Fe 3 (CO) 12. • Electrochemical investigation of [FeFe]-hydrogenase mimics. • Investigate the catalytic activity of [FeFe]-hydrogenase mimics in the presence of acetic acid. In this report, the influence of the substitution decoration in ferrocenyl selenophen-2-yl thioketone (1) and ferrocenyl furan-2-yl thioketone (2) utilized as a proligand in complexation reactions with Fe 3 (CO) 12 was examined. As a result, three new complexes, considered [FeFe]-hydrogenase mimics, were prepared and characterized by IR, 1H, 13C{1H}, and 77Se{1H} NMR spectroscopy, mass spectrometry, elemental analysis, and X-ray single-crystal diffraction methods. Moreover, the obtained complexes were compared with the analogous ferrocenyl α-thienyl thioketone as a starting material. Respectively, the reaction of compound 1 with Fe 3 (CO) 12 is found to give two complexes that have similar structures to those obtained in analogous reactions with ferrocenyl α-thienyl thioketone. Conversely, compound 2 gives only an α,β-unsaturated aldehyde moiety as a result of the furan ring being opened. Furthermore, the electrochemical properties of the resulting complexes were investigated using cylic voltammerty in the absence and presence of acetic acid (AcOH) as a proton source and compared with their structurally related thiophene derivative. Accordingly, the nature of the linkage of these synthetic approaches has a significant effect in determining its redox properties. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, we describe a very fast and efficient synthesis of series of new Schiff bases L1-L5 derived from benzimidazole. It was found that, these compounds react efficiently with mercury ions to afford the corresponding complexes COP1-COP5 in nearly quantitative yield. This reaction takes place in water and in most of the usual solvents. The study of the complexation reaction of L1 with other metal ions has been carried out and shown that L1 can efficiently coordinate with Cu2+ and Co2+. In addition, the reactivity of the benzimidazole Schiff bases has been compared with some reported pyridine analogues and checked with DFT calculations. It has been found that both experimental results and theoretical calculations confirm that the benzimidazole Schiff bases are clearly more reactive than their pyridine analogues. Image 1 • A new series of Schiff bases derived from benzimidazole has been synthesized. • Their coordination behavior toward mercury ions has been studied. • Molecular structure of the obtained mercury complexes has been established. • The complexation of the Schiff bases with other metal ions has been carried out. • A comparative study has been performed by means of DFT calculations. [ABSTRACT FROM AUTHOR]

Abstract The new series of divalent metal complexes [M(ox)(thy) 2 ]; M = Cd2+, Ni2+, Mn2+, Fe2+, Cu2+ and Zn2+, with mixed ligands oxalato (ox) and theophylline (thy) were prepared and characterized by molar conductance, FT-IR, UV–visible, 1H and 13C NMR and X-ray structure analysis. The crystal structure including the positions of the Zn (II) complex was determined by powder diffraction analysis using the FOX program. In the structure of zinc complex, the zinc (II) cations are octahedrally coordinated by two terminals N-bonding for theophylline ligand and by the O atoms of two oxalato bidentate ligand, resulting in discrete and slightly distorted octahedral complex. This complex was crystallized in the monoclinic system (C1 2/c1) space group and the unit cell parameters are a = 11.8364(1)Å, b = 4.5200(1)Å, c = 9.9942(1)Å with β (°) = 126.4770(2)°. The antimicrobial activity of the complexes was studied and the results of their tests show that the metal (II) complexes are more effective against several of bacterial and fungal strains. Graphical abstract Image Highlights • Six new complexes of general formula:[M (ox)(thy) 2 ] were synthesized. • The characterization of the synthesized complexes was investigated. • The octahedral structure of the obtained complexes was checked. • The antibacterial activity of the complexes was tested. [ABSTRACT FROM AUTHOR]

In this work correlation dependencies between hydrogen bond energy Δ E for complexes with F H⋯F hydrogen bond and their spectroscopic characteristics of the IR and NMR spectra are presented. We considered 26 complexes in a wide hydrogen bond energy range 0.2–47 kcal/mol. For each complex we calculated complexation energy (MP2/6-311++G(d,p)), IR spectroscopic parameters (FH stretching frequency ν , FH stretching frequency in local mode approximation ν LM at MP2/6-311++G(d,p) level) and NMR parameters (chemical shift of hydrogen δ H and fluorine nuclei δ F , Nuclear Independent Chemical Shielding and spin-spin coupling constants 1 J FH , 1h J H...F , 2h J FF at B3LYP/pcSseg-2 level). It was shown that changes of parameters upon complexation, i.e. changes of the stretching frequency in local mode approximation Δ ν LM , change of the proton chemical shift Δ δ H and change of the absolute value of spin-spin coupling constant 1 J FH could be used for estimation of corresponding hydrogen bond strength. Furthermore, we build correlation dependencies between abovementioned spectroscopic characteristics and geometric ones, such as the asymmetry of bridging proton position q 1  = 0.5·( r FH – r H…F ). [ABSTRACT FROM AUTHOR]

Lurasidone hydrochloride (LHD) is an atypical antipsychotic drug has poor aqueous solubility and low bioavailability (9–19%). This study describes effect of different methods of complex formation with β-cyclodextrin (BCD) on enhancement of dissolution and on antidepressant, antipsychotic effects of LHD. Other purpose of this study is to compare pharmacodynamic effects of complexes with that of self microemulsifying drug delivery system of LHD (SMEDDS). Inclusion complexes (IC) of LHD and BCD were prepared by physical mixing (PM), kneading (KN) and spray drying (SD) in a 1:1 M ratio. These complexes were characterized by different techniques. KN and SD showing enhancement in dissolution, were compared with SMEDDS using Forced swim test (FST) and Tail suspension test (TST) for antidepressant action and Paw test for antipsychotic activity. Characterization of complexes confirmed interaction between LHD and BCD. Enhancement in dissolution is seen in following order SD > KN > PM > LHD. In all three animal models, SD, KN and SMEDDS showed statistically significant effect (p < .05) than drug alone showing enhancement in bioavailability. Complexation of LHD with BCD enhances dissolution which reflected in improvement of antidepressant and antipsychotic activity of drug. Solubility enhancement methods like complexation and self microemulsion improves pharmacodynamic activities of drug. Improvement of pharmacodynamic effect is seen in order, SD ≥ SMEDDS ≥ KN > LHD. [ABSTRACT FROM AUTHOR]

In this work, we studied the complexation mode between copper(II) ion and the specific ligand investigated as carriers of metals though biological membranes, diethyldithiocarbamate (Et 2 DTC). It is important to understand how this occurs because it is an important intracellular chelator with potential therapeutic applications. Theoretical and experimental UV visible studies were performed to investigate the complexation mode between copper and the ligand. Electrochemical studies were also performed to complement the spectroscopic analyses. According to the theoretical calculations, using TD-DFT (Time dependent density functional theory), with B3LYP functional and DGDVZP basis set, implemented in Gaussian 03 package, it was observed that the formation of the complex [Cu(Et 2 DTC) 2 ] is favorable with higher electron density over the sulfur atoms of the ligand. UV/Vis spectra have a charge transfer band at 450 nm, with the DMSO-d6 band shift from 800 to 650 nm. The electrochemical experiments showed the formation of a new redox process, referring to the complex, where the reduction peak potential of copper is displaced to less positive region. Therefore, the results obtained from this study give important insights on possible mechanisms involved in several biological processes related to the studied system. [ABSTRACT FROM AUTHOR]

Four new complexes based on the 4-(4-carboxyphenyl)-1,2,4-triazole (Hcpt) ligand, {[Co(cpt) 2 (H 2 O) 4 ]·H 2 O}( 1 ), {[Cr(cpt) 2 (H 2 O) 4 ]·10H 2 O}( 2 ), {[Fe(cpt) 2 (H 2 O) 4 ]·10H 2 O}( 3 ), {[Zn(cpt) 2 (H 2 O) 2 ]}( 4 ) have been synthesized and characterized by elemental analysis, single crystal X-ray diffraction and TGA. For complexes 1 , 2 , and 3 , they almost have the same coordination mode that only one nitrogen atom of triazole are involved in the coordination, while in the complex 4 , only the group COO − participates in the coordination. In the crystal structure of 1 , each structural unit[Co(cpt) 2 (H 2 O) 4 ] is linked to another by hydrogen bonding formed by the lattice water molecules, thus forming a one-dimensional chain structure; In the crystal structure of 2 or 3, each structural unit[Cr(cpt) 2 (H 2 O) 4 ] or [Fe(cpt) 2 (H 2 O) 4 ] forms a two-dimensional layered structure by intermolecular hydrogen bonds from the coordinated water molecule and the group COO − . The results of thermogravimetric analysis show that the loss of lattice water and coordinated water molecules in 1 , 2 and 3 is below 120 °C, while the loss of coordinated water molecules in 4 is in the temperature range of 190–260 °C. Hirshfeld surface shows that the N H⋯O hydrogen bonding interaction plays a significant role towards the conformation of the basic structure of these complexes. [ABSTRACT FROM AUTHOR]

The ability of Captisol ® (sulphobutylether-β-cyclodextrin, SBE-β-CD), to form inclusion complexes, both in solution and in the solid state, has been tested in order to improve some unfavorable chemical-physical characteristics, such as poor solubility in water, of a bioflavonoid, Coumestrol (Coum), well known for its anti-oxidant, anti-inflammatory, anti-fungal and anti-viral activity. In pure water, a phase-solubility study was carried out to evaluate the enhancement of the solubility of Coum and, therefore, the occurred complexation with the macrocycle. The stoichiometry and the stability constant of the SBE-β-CD/Coum complex were calculated with the phase solubility method and through the Job's plot. After that, the solid SBE-β-CD/Coum complex was prepared utilizing a kneading method. The spectral changes induced by complexation on characteristic vibrational band of Coum were complementary investigated by Fourier transform infrared spectroscopy in attenuated total reflectance geometry (FTIR-ATR) and Raman spectroscopy, putting into evidence the guest chemical groups involved in the “host-guest” interactions responsible of the formation and stabilization of the complex. Particular attention was paid to the C O and O H stretching vibrations, whose temperature-evolution respectively furnished the enthalpy changes associated to the binding of host and guest in solid phase and to the reorganization of the hydrogen bond scheme upon complexation. From the whole set of results, an inclusion geometry is also proposed. [ABSTRACT FROM AUTHOR]

Aromatic diamides, derivative of 2,6-pyridinedicarboxylic acid and isophthalic acid, bearing 1,3,4-thiadiazole residue were prepared with satisfactory yields in conventional procedures and microwave stimulated reactions. X-ray structure of N , N ′-bis(1,3,4-thiadiazol-2-yl)-2,6-pyridinedicarboxamide ( 2 ) DMSO solvate ( 2 ·DMSO) was described. Selective zinc(II), lanthanum(III), terbium(III) and l -tyrosine recognition was found for N , N ′-bis(1,3,4-thiadiazol-2-yl)-2,6-pyridinedicarboxamide in DMSO and its mixture with water. The IDA (Indicator Displacement Assay) system for metal cations sensing was proposed. The binding properties of 2 were compared with newly synthesized N , N ′-bis(1,3,4-thiadiazol-2-yl)-1,3-benzenedicarboxamide 1 . [ABSTRACT FROM AUTHOR]

Metal coordination by spironaphthopyran derived merocyanines bearing benzazol substituents has been studied by means of experimental and theoretical methods. The formation of N-O coordinated chelate complexes have been observed by means of X-ray diffraction. Merocyanine scaffolds of these complexes possess trans-trans-cis conformation independently of both substituents in positions 1 and 5 of indoline moiety and benzazole heteroatom. Stability of merocyanine-metal complexes significantly depends on two factors: relative thermodynamic stability of spirocyclic and open isomers and complexation energy. Variation of the ligand structure involving chelating group significantly changes stability of complexes while replacement of the substituents in the indoline ring peripheral to the chelating parts of the molecules and biasing the spiropyran – merocyanine equilibrium provide the fine tuning of complexation selectivity. Complexes of diamagnetic ions (Mg 2+ , Zn 2+ , Cd 2+ ) undergo photodissociation. The complexes of benzoxazole containing ligands demonstrate higher quantum yields comparing to their benzothiazole analogue. [ABSTRACT FROM AUTHOR]

The isolation of reaction products of asparagine with reducing sugars at alkaline pH and high temperature has been probed by a combination of high performance liquid chromatography (HPLC) coupled with a Fraction Collector. The UV–vis and FTIR spectra of the isolated Maillard reaction products showed structure-sensitive changes as depicted by deamination events and formation of asparagine-saccharide conjugates. The initial reaction species of the Asn-Gluc reaction were also characterized by Density Functional Theory (DFT) methods. Evidence for Cu (II) metal ion complexation with the Maillard reaction products is supported by UV–vis and FTIR spectroscopy. [ABSTRACT FROM AUTHOR]

Cyclodextrin conjugate complexation is a useful method to enhance the solubility and absorption of poorly soluble drugs. A series of new Rhein-β-cyclodextrin conjugates (Rh-CD conjugates) have been synthesized and examined. Rhein is covalently linked with the β-CD by amido linkage in a 1:1 molar ratio. The conjugates were characterized by 1 H NMR, 13 C NMR, HRMS, powder X-ray diffraction (powder XRD) as well as thermogravimetric analysis (TGA). The results reveal that incorporation of β-CD could improve the aqueous solubility of Rhein and the cytotoxicity against hepatocellular carcinoma (HepG2) cell line as well as antibacterial activity against three organisms. The improved biological activity and the satisfactory water solubility of the conjugates will be potentially useful for developing novel drug-cyclodextrin conjugates, such as herbal medicine. [ABSTRACT FROM AUTHOR]

We have reported the synthesis involving the condensation of pyridoxal with tris(2-aminoethyl)amine obtained a tripodal ligand, as well as its subsequent complexation with the manganese(II) and nickel(II) ions. The structural analysis revealed, in the case of complex 1 , the formation of a monomeric complex with Mn(II) species. In the complex 2 , with Ni(II) metal ion, we describe the probable mechanism for the formation of hemiacetal in these complexes. Only the complex 1 catalyze the dismutation of superoxide efficiently with IC 50 equal to 3.38 μM, evaluated through the nitro blue tetrazolium photoreduction inhibition superoxide dismutase assay, in aqueous solution of pH 7.8. Density functional theory calculations are done to characterize and compare the molecular frontier orbitals of the Mn(II) and Ni(II) complexes. [ABSTRACT FROM AUTHOR]

Complexation of two 1,3-alternate calix[4]crown ligands with alkali metals (K + , Rb + and Cs + ) has been investigated by electrospray ionization mass spectrometry (ESI-MS) and density functional theory calculations. The binding selectivities of the ligands and the binding constants of their complexes in solution have been determined using the obtained mass spectra. Also the percentage of each formed complex species in the mixture of each ligand and alkali metal has been experimentally evaluated. For both calix[4]crown-5 and calix[4]crown-6 ligands the experimental and theoretical selectivity of their alkali metal complexes found to follow the trend K + > Rb + > Cs + . The structures of ligands were optimized by DFT-B3LYP/6-31G method and the structures of complexes were obtained by QM-SCF-MO/PM6 method and discussed in the text. [ABSTRACT FROM AUTHOR]

Thermodynamic parameters (Δ G , Δ H , and T Δ S ) for the complexation of mono(3-deoxy-3-guanidino- altro )-α-cyclodextrin ( 1 ) or mono(3-deoxy-3-guanidino)-α-CD ( 2 ) with p -nitrophenolate ion were determined by 1 H NMR titration experiments in D 2 O solution containing 0.10 mol dm −3 Na 2 CO 3 –NaHCO 3 at 298, 308, 318, and 328 K, to investigate the effect of the macro ring flexibility of 1 on the complexation with the planar guest. Both Δ H and T Δ S values for the inclusion complexation of 1 with the guest (−39.6 kJ mol −1 and −23.3 kJ mol −1 , respectively) decreased more than those for 2 with the guest (−27.6 kJ mol −1 and −10.0 kJ mol −1 , respectively). This fact suggested that the degree of freedom of the guest and the flexibility of the macro ring of 1 were decreased by the tight binding of the guest in the manner of induced fit. The existence of anisotropic ring current effect by the guest on the 1 H NMR signals for C(3)- and C(5)-H's of 1 confirmed that the molecular rotation of the guest is retarded in the complex of 1 with p -nitrophenolate ion. The molecular orientation of the guest in the inclusion complex with 1 was determined by means of ROESY (rotating-frame overhauser effect spectroscopy) experiment. [ABSTRACT FROM AUTHOR]

The reactivities of (9′-fluorene)-spiro-5-hydantoin and its thio-analogue with Cu(II) were studied in different reaction conditions and the formed products were characterized by spectroscopic methods (IR, NMR and/or EPR). It was found that unlike the 2,4-dithio- analogue, both the (9′-fluorene)-spiro-5-hydantoin and its 2-thio derivative form Cu(II) complexes only in presence of a strong base. We identified the coordination mode of the ligands and the structure of the complexes through geometry optimization of different models and calculations of the corresponding spectroscopic parameters using ab initio quantum chemical methods. The comparison between the experimental and the theoretical data suggested monodentate coordination of the fluorene-hydantoin ligands after deprotonation of one amido group. Additional confirmations of this proposition were obtained from the experimental and DFT-calculated EPR parameters (g-factor and A-tensor), which allowed for determination of the most probable geometry of the complexes. We further employed the quantum chemical methods to explain the observed differences in the complexation abilities of variously spiro-5-substituted thio- and dithio-hydantoins, accounting for the structural effects on the electron density and acidity of the hydantoin ring. [ABSTRACT FROM AUTHOR]

Anion complexation of benzene capped flexible tripodal receptor and solid state stabilization of discrete hybrid anion-water or infinite water clusters by various supramolecular interactions are reported here. The crystal structure of the receptor in protonated states shows all the three arms projected in one direction. We structurally demonstrate discrete fluoride-water cluster [F 2 –H 2 O] 2− and square shaped chloride-water cluster [Cl 2 –(H 2 O) 2 ] 2− inside the cationic channel of the receptor. Structural analysis also reveals that these clusters are stabilized inside the channel through active participation of N/C/Ow′H⋯Ow, N/C/Ow′H⋯X − (X − = F − , Cl − and I − ) H-bonds and electrostatic interactions. Moreover, C–H⋯π and π⋯π types weak intermolecular interactions appear to play crucial role in supramolecular assembly of receptor. Additionally, on treatment with hydroiodic acid (HI) L resulted zwitterionic iodide complex. Crystal structure reveals the presence of S···I halogen bonded dimer, I 2 ···I halogen bond, 1D infinite water chain and neutral iodine molecules. It is comprehensible that ligand basal structure (benzene capped and N-bridge head in two tripodal) play crucial roles in the formation of diverse halide-water cluster. All structures were well examined by different techniques such as NMR, IR, TGA, DSC, PXRD and XRD. [ABSTRACT FROM AUTHOR]

• Two 2-D and 3-D supramolecular Ni(II) and Co(III) complexes based on 3-ethoxy salicylaldehyde were structural characterized. • X-ray crystallography revealed that the valence of cobalt ion is trivalent, EPR and cyclic voltammetry experiment also proved the result. • The experimental investigations match with those obtained from TD-DFT calculations. • ESP calculation results confirmed the charge distribution in the molecule and Hirshfeld surface analyses of complexes 1 and 2 were also discussed. The ligand 2-(3-ethoxy-2-hydroxyphenyl)-4-methyl-1,2-dihydroquinazolin 3-oxide (HL1 , H is the deprotonatable hydrogen) has been synthesized, and two metal complexes, namely [Ni(L2) 2 ]·2CH 3 OH (1) and [Co(L2) 2 ]·NO 3 ·H 2 O (2) (where HL2 =1-(2-{[(E)-(3- ethoxy -2- hydroxybenzylidene ]amino} phenyl)ethanone oxime) were obtained via complexation reaction between HL1 and nickel(II) acetate tetrahydrate or cobalt(II) nitrate hexahydrate. HL1 and both complexes were characterized by elemental analysis, as well as compared by spectroscopic methods such as FT-IR, UV–Vis and fluorescence spectroscopy. X-ray crystallography revealed that both complexes have distorted octahedral geometries but with a different configuration of the two tridentate (L2)– ligands around the metal centers. Complex 1 contained two lattice methanol molecules whereas 2 were counterbalanced by a nitrate anion beside an uncoordinated water molecule. The crystal structures show a 2-D and 3-D supramolecular architecture due to intermolecular interaction. Electrochemical properties of both complexes were tested by cyclic voltammetry and Electron paramagnetic resonance (EPR) spectroscopy of 2 was also investigated. Fascinatingly, antibacterial efficiencies of all compounds were compared. Furthermore, molecular electrostatic potential (ESP) was computed for both complexes to predict the reaction sites of electrophilic and nucleophilic attacks. Density Functional Theory (DFT) calculations were done to ascertain the optimum geometric configurations. The non-covalent interaction was determined using the Hirshfeld program. The quinazoline-type ligand HL1 , used for the synthesis of two discrete metal complexes, [Ni(L2) 2 ]·2CH 3 OH (1) and [Co(L2) 2 ]·NO 3 ·H 2 O (2), was observed to be modified upon complexation with HL2. Both complexes were characterized by X-ray crystallography, spectroscopic methods such as FT-IR, UV–Vis and fluorescence spectroscopy, and electrochemical properties, as well as Hirshfeld surface analysis and DFT studies. The antimicrobial activities of all compounds were also compared. [Display omitted] [ABSTRACT FROM AUTHOR]

• Synthesis and characterization of Cu(II), Fe(III) and Zn(II) complexes. • Effective coordination of the pharmac to only one complex, the Zn(II) complex. • Analysis by DFT calculation of the reactions between these complexes and NaSDZ. • Effect of the lability of chloro and stabilization of HOMO are presented. • Initial anti-toxoplasma study is presented. Toxoplasmosis is an endemic neglected disease spread throughout the southern hemisphere, affecting a large part of the population concentrated in these countries. Aiming to develop new coordination compounds with anti-toxoplasma activity, we report herein the reactions between the mononuclear complexes [Cu(HL1)Cl 2 ] (1) , [Fe(HL1)Cl 3 ] (2) , and [Zn(HL1)Cl 2 ] (3) (HL1 is the ligand N-2[(pyridine-2-ylmethyl)amino)ethanol)) and sodium sulfadiazine (NaSDZ), one of the current drugs used to treat toxoplasmosis. DFT data suggested that complexation reactions between complexes (1) - (3) and NaSDZ result in stable complexes (4)-(6) , containing SDZ− in their coordination spheres, based on EDA (Energy Decomposition Analysis), which indicate favorable interaction between the metallic centers of the complexes and the anion SDZ−. The EDA results also suggest that the SDZ− anion donates negative charge to the metal, weakening the M-Cl interaction, present in complexes (1)-(3) , and making the coordination with SDZ− anion easier. However, the reactions of (1) and (2) with NaSDZ were indeed ineffective, then complexes (4) and (5) were not obtained. Only the formation of [Zn(HL1)(SDZ)Cl].2H 2 O (6) was achieved, the product of the reaction between complex (3) and NaSDZ. Further analysis of DFT calculations and EDA data were carried out to understand the lack of the reactivity of compounds (1) and (2). The data revealed higher lability for the chloro ligand present in complex (3) and better stabilization of complex (6) 's HOMO. Steric and stacking effects could also justify these experimental data. This parallel theoretic-experimental study allowed us to conclude that complex (6) is the most probable to be obtained synthetically, in agreement with the experimental behavior. Furthermore, a complete characterization employing spectroscopic and electrochemical is presented for all the complexes, with and without SDZ− anion, including X-ray diffraction studies for complexes (1) and (6). The cytotoxic effects on T. gondii infecting LLC-MK2 host cells are presented and indicate that all the complexes reduced the parasite´s ability to proliferate. These results suggest that these compounds are promising, especially complex (2) , which causes the death of the parasite. [ABSTRACT FROM AUTHOR]

Inclusion complexes of diclofenac sodium (DS) with β–cyclodextrin (β–CD) were prepared in order to improve the solubility, dissolution and oral bioavailability of the poorly water soluble drug. The effect of method of preparation of the DS/β−CD inclusion complexes (ICs) was investigated. The ICs were prepared by microwave irradiation and also by the conventional methods of kneading, co-precipitation and freeze drying. Though freeze drying method is usually referred to as the gold standard among all the conventional methods, its long processing time limits the utility. Microwave irradiation accomplishes the process in a very short span of time and is a more environmentally benign method. Better efficacy of the microwaved inclusion product (MW) was observed in terms of dissolution, antimicrobial activity and antibiofilm properties of the drug. Thus microwave irradiation can be utilized as an improved, time-saving and cost-effective method for the generation of DS/β–CD inclusion complexes. [ABSTRACT FROM AUTHOR]

Cerium-triethanolamine complex was synthesized by simple complexation method in 1-propanol solvent using cerium(III) chloride as a metal source and triethanolamine as a ligand. The structures of the prepared complex were proposed based on FT-IR, FT-Raman and ESI-MS results as equimolar of triethanolamine and cerium chelated complex having monomeric tricyclic structure with and without chloride anion as another coordinating group known as ceratrane. The complex was used as a precursor for ceria material done by thermal decomposition. XRD result revealed that when calcined at 600 °C for 2 h, the cerium complex was totally turned into pure ceria with cubic fluorite structure. The obtained ceria was then employed to synthesize platinum doped ceria catalysts for methane steam reforming. Various amounts of platinum i.e. 1, 3, 5 and 10 mol percents were introduced on the ceria support by microwave-assisted wetness impregnation using ammonium tetrachloroplatinate(II). The platinum-impregnated ceria powders were subjected to calcination in 10% hydrogen/helium atmosphere at 500 °C for 3 h to reduce platinum(II) to platinum(0). XRD patterns of the catalysts confirmed that the platinum particles doped on the ceria support were in the form of platinum(0). Catalytic activity test showed that the catalytic activities got higher as the amounts of platinum doped increased. Besides, the portions of coke formation on the surface of catalysts were reduced as the amounts of platinum doped increased. [ABSTRACT FROM AUTHOR]

The Fourier transform IR and Raman spectra of the zero generation dendrimer G 1 with two P N P S linkages and four terminal aldehyde groups have been recorded. The optimized geometry of low energy isomer of G 1 have been calculated by density functional (DFT) method at the PBE/TZ2P level of theory. DFT is used for analyzing the properties of P N P S linkages. DFT results for the structure of G 1 are in good agreement with X-ray diffraction measurements. A complete vibrational assignment is proposed for different parts of G 1 . The global and local reactivity descriptors have been used to characterize the reactivity pattern of the core function and terminal group. Natural bond orbital (NBO) analysis has been applied to comparative study of charge delocalization. Our study reveals that the softness and electrophilicity of sulfur atom in the core of the dendrimer G 1 is higher than that of sulfur atoms and of the dendron G 2 . Thus P N P S linkage has a high electron density on sulfur which allows the regiospecific complexation of gold, whereas the other P S groups do not react this way. This explains why P N bond in P N P S linkage is much more stable than isolated P N bonds, which are easily hydrolyzed. [ABSTRACT FROM AUTHOR]

Benchmark calculations of 15 N NMR shielding constants for a set of model complexes of rhodium(II) tetraformate with nine organic ligands using the Density Functional Theory (DFT) methods have been carried out. The calculations were performed by means of several methods: the non-relativistic, relativistic scalar ZORA, and spin-orbit ZORA approaches at the CGA-PBE/QZ4P theory level, and the GIAO NMR method using the B3PW91 functional with the 6-311++G(2d,p) basis set for C, H, N, O atoms and the Stuttgart basis set for the Rh atom. The geometry of compounds was optimised either by the same basis set as for the NMR calculations or applying the B3LYP functional with the 6-31G(2d) basis set for C, H, N, O atoms and LANL2DZ for the Rh atom. Computed 15 N NMR shielding constants σ were compatible with experimental 15 N chemical shifts δ of complexes exhibiting similar structure and fulfil the linear equation δ = aσ + b . The a and b parameters for all data sets have been estimated by means of linear regression analysis. In contrast to the correlation method giving “scaled” chemical shifts, the conversion of shielding constants to chemical shifts with respect to the reference shielding of CH 3 NO 2 provided very inaccurate “raw” δ values. The application of the former to the calculation of complexation shifts Δ δ (Δ δ = δ compl − δ lig ) reproduced experimental values qualitatively or semi-quantitatively. The non-relativistic B3PW91/[6-311++G(2d,p), Stuttgart] theory level reproduced the NMR parameters as good as the more expensive relativistic CGA-PBE//QZ4P ZORA approaches. [ABSTRACT FROM AUTHOR]

The parent 1,3,5-triacetyl-2,4,6-trihydroxybenzene was prepared in up to 91% yield using a one-pot, one step reaction catalyzed by aluminum chloride. Its alkylations with 1,5-dibromopentane generated a symmetric tripodal hexasubstituted benzene precursor in the alternated conformer predicted by a theoretical calculation. Subsequent substitutions and reductions provided the corresponding tris-amine in 59% yield. Aminations of the tripodal precursor with ( R )-(+)-1-phenylethylamine obtained a chiral tris-amine ligand in 44% yield. 1 H NMR titrations of this ligand with each of three l -amino acid derivatives as guest molecules confirmed the presence of their complexes, in which the complex with alanine derivative displayed the strongest interactions with the ligand. Job plots suggested that all complexes composed of 1:2 ratios of the ligand and these guests. Theoretical calculations additionally revealed the structures and the associated binding parameters of the complexes. [ABSTRACT FROM AUTHOR]

The purpose of this research was to investigate the inclusion complex formation between 4,4′-methylene-bis(N,N-dimethylaniline) (MBDA) and β-cyclodextrin (β-CD). The inclusion complex of MBDA and β-CD was characterized both in solution and solid state by UV–Visible spectroscopy, fluorescence spectroscopy, Differential Scanning Calorimetry (DSC), Fourier Transform Infra-red spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), Powder X-ray diffractometry (XRD) and Atomic Force Microscopy (AFM). The solid inclusion complex was prepared by co-precipitation method. The 1:1 stoichiometry of inclusion complex and binding constant were determined by Benesi–Hildebrand plot and was confirmed by Jobs continuous variation method. The spectral shifts revealed that only a part of MBDA molecule is entrapped in the β-CD cavity. Nanosecond time resolved fluorescence study revealed that MBDA exhibits single exponential decay in aqueous medium and bi-exponential decay in β-CD medium indicating the formation of 1:1 inclusion complex. The Gibbs free energy change of the complexation process was determined and it was found that the inclusion complexation process was spontaneous. The most probable structure of the inclusion complex of MBDA and β-CD was proposed based on the molecular docking study. [ABSTRACT FROM AUTHOR]

• The nanostructure thin films [Az]TF and [Az/Pd]MNC were fabricated using the spin coating technique. • Characterization and optical properties of the fabricated [Az]TF and [Az/Pd]MNC nanostructured thin film. • Average crystallite sizes are 64.30 nm and 97.65 nm for [Az]TF and [Az/Pd]MNC respectively. • The average crystallite size (D a v), and energy gaps (E I n d i r O p t. and E D i r O p t. ) determined of [Az]TF and [Az/Pd]MNC. • Geometry study of [Az] and [Az/Pd]MNC as an isolated molecule using TD-DFT/DMOl3 and TD-DFT/CASTEP methods. • the optical conductivity ration σ 2 (h ν) / σ 1 (h ν) is 3.03 × 107 at a photon energy of 2.98 eV. Azithromycin (Az) is a novel macrolide antibiotic with better activity against intracellular gramme negative bacteria and has been routinely prescribed for the treatment of respiratory tract infections in addition to its efficacy and safety. Azithromycin behaves as a bidentate ligand for complexation reactions that have an (O, N) atom donor. The goal of this research was to develop an azithromycin-palladium mono nanocomposite [Az/Pd]MNC with suitable physicochemical properties. [Az] loaded Pd (II) nanoparticles (NPs) were produced using a nano-precipitation process in three different drug-to-Pd (II) ratios. The drug to metal ratio affects physicochemical parameters, according to the findings. Nanoscale size particles ranging from 53.86, 94.09 to 76.09, 106.38 nm were attained for [Az]TF and [Az/Pd]MNC respectively, according to the results of XRD examination. Physicochemical properties were affected by drug to metal ratio. At a molecular level, FT-IR spectroscopy revealed observable interactions between the medication and [Pd]NPs. The TEM electron microscopy morphology investigations showed that the formed [Az/Pd]MNC nanoparticles are of sphere shapes microporous as well as needle shapes with an average diameter of about 84.3 nm. For the crystal models and isolated molecules, the materials Studio 7.0 program on TDDFT/DMol3 was used to optimize the molecular structure and perform frequency calculations which, the potential of electrostatic molecular (MEP) in three dimensions for the [Az/Pd]MNC showed that the potential range of Az and the Az-Pd complex is -7.609 × 10−2 V ≥ potential ≥ 7.609 × 10−2 V and -8.201 × 10−2 V ≥ potential ≥ 8.201 × 10−2 V, respectively. The number and character of molecular orbitals can be determined using electron density (ED) as a function of energy. The DFT-Gaussian09W-vibration values are quite similar to the experimental data either in the structure or in the optical properties. In conclusion, the mono nanocomposite of azithromycin palladium preparations showed appropriate physicochemical and optical properties and their new results are subsequently discussed in detail, as well as it is promising for use in solar cell applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Highlights: [•] Two dinuclear Cd(II) complexes are assembled from quinoline-based carboxylic acids. [•] They show hydrogen-bonding driven 3D framework with dia topology. [•] Luminescent and antibacterial properties of all compounds were investigated. [•] Complexes show higher activities due to the increased lipotropism on complexation. [Copyright &y& Elsevier]

Highlights: [•] Stability of the Na+ – sodium ionophore III complex was determined. [•] Quantum mechanical DFT calculations were carried out. [•] Structures of the nonhydrated and hydrated cationic complexes were predicted. [Copyright &y& Elsevier]

Highlights: [•] Ephedrine assessment based on charge–transfer complexation. [•] The newly synthesized complexes have been characterized spectroscopically. [•] The physical spectroscopic data have been determined using the Benesi–Hildebrand method. [•] Thermal decomposition behavior of these complexes was studied. [•] The kinetic thermodynamic parameters were calculated. [ABSTRACT FROM AUTHOR]

Highlights: [•] Complexation of rhodium(II) salts with heteroaromatic N-oxides with various functionalities was studied by NMR spectroscopy. [•] GIAO NMR DFT calculations of NMR chemical shifts and complexation shifts of adducts were performed. [•] Calculated and experimental NMR complexation shifts were applied to establishing the complexation site in ligands. [ABSTRACT FROM AUTHOR]

• Five new alkali metal complexes (1 – 5) with nirogen and oxygen donor ligands have been synthsized and charcterized by infrared and UV–vis spectroscopy, elemental analysis, 1H NMR, and single-crystal X-ray diffraction analysis. • The complexes displayed excellent activities against oral and lung cancer cells with the least toxicity toward normal cells. In this report, we present five new alkali metal complexes (1 – 5) that displayed excellent anticancer and antibacterial activities in solutions. 1,10-phenanthroline (phen), salicylic acid (sa) benzoic acid (ba), and p-aminobenzoic acid (paba) ligands were employed in complexation reactions. The complexes were characterized by a variety of analytical techniques including infrared and UV–vis spectroscopy, elemental analysis, 1H NMR, 13C NMR, and single-crystal X-ray diffraction analysis. We described the structures of three mononuclear lithium complexes [Li(phen) 2 (sal)] (1), [Li(phen) 2 (ba)] (2), {[Li(phen)(H 2 O) 3 ].(paba)} (3), a mononuclear sodium complex [Na(phen)(paba)(H 2 O)] (4) and an unsual tetranuclear cesium complex [Cs 4 (phen) 4 (paba) 4 (H 2 O) 2 ] (5). The complexes in solution displayed excellent activities against oral and lung cancer cells with the least toxicity toward normal cells when compared to the standard drug 5-fluorouracil and cisplatin. [Display omitted] [ABSTRACT FROM AUTHOR]

Schiff bases L1 [i.e., 2-(diphenylphosphino)-N-(naphthalen-1-ylmethylene)ethanamine], L2 [i.e., 2- (diphenylphosphino)-N-(naphthalen-2-ylmethylene)ethanamine], L3 [i.e., 2-(1-(2-(diphenylphosphino)ethylim- ino)ethyl)naphthalen-1-ol] and L4 [i.e., 2-((2-(diphenylphosphino)ethylimino)methyl)naphthalen-1-ol] have been synthesized using a straightforward methodology which involves a condensation reaction between H 2 N−CH 2 −CH 2 −PPh 2 and appropriate carbonyl compound. Due to the presence of diphenylphosphine (−PPh 2) moiety and >C = N− functionality, these compounds behave as ligands and undergo complexation reaction with palladium on treatment with Na 2 PdCl 4 to yield the palladium(II) complexes (1–4). Ligands as well as complexes have been characterized using standard NMR spectroscopic techniques. ESI−MS and single crystal X−ray diffraction studies corroborate the structures of complexes. Crystal structures of complexes 1−3 reveal clearly that the geometry around Pd centre is distorted square planar. Ligands L1 and L2 are coordinated to Pd centre in bidentate (P, N type) mode, however, L3 and L4 act as a tridentate (P,N,O type) ligand and bind with metal in anionic mode. The Pd P and Pd N bond distances in complexes 1−3 are in the ranges 2.204−2.212 Å and 2.023−2.072 Å, respectively. Complex 3 [i.e., PdCl(L3 −H)] also has a Pd-O bond, the length of which is found to be 2.009(3) Å. All the complexes have potential for catalysing O-arylation (C-O coupling) of phenol and Suzuki-Miyaura coupling (SMC) reactions. Both bromoarenes and chloroarenes can be used as substrates in Suzuki coupling and converted into biaryl derivatives. For O-arylation reactions of phenol, bromoarenes are used as arylating agents. For catalysis of such reactions (i.e., C-O coupling), high (0.1 mol%) catalyst loading is required. However, Suzuki reactions require low (0.001 mol%) loading of catalysts to occur with bromoarenes and give the products. The high potential of the complexes is also evident from the fact that they also convert different aryl chlorides into the coupled products in Suzuki coupling. 31P{1H} NMR data reveal that the electronic environments of nuclei of phosphorous donors are closely similar in all the four ligands. Similar magnitude of deshielding of the 31P{1H} signals in all the complexes indicate that, while forming the dative bond, the P donor of all the ligands transfer the electron density to the palladium to a similar extent. Hence, the electronic effects created by the ligands through the phosphorous donor are similar in all the complexes. Therefore, it is inferred that variation in their catalytic performance is because of difference in the binding mode of the ligand and/or minor alteration in the architecture of organic ligand. Amongst them, complex 2 shows the highest catalytic activity, and the least active catalyst is complex 3 for C-C coupling reactions. For C-O coupling reactions, the efficiencies of complexes 1 and 2 are slightly higher than those of complexes 3 and 4. [ABSTRACT FROM AUTHOR]

Highlights: [•] Inclusion complexes of SFP with α- and β-cyclodextrin were investigated. [•] SFP drug formed 1:1 complex with α-CD and β-CD at pH∼6.5. [•] Complex formation was confirmed by FTIR, DSC, SEM, 1H NMR, XRD and PM3 methods. [•] Part of pyridine ring of SFP is present inside the CD nanocavity. [•] Nanoparticles were observed from drug–CD complex in the presence of water by TEM. [Copyright &y& Elsevier]

Abstract: Boronic acids are a class of intensively explored compounds, which according to their specific properties have been intensively explored in last decades. Among them phenylboronic acids and their derivatives are most frequently examined as receptors for diverse carbohydrates. In turn, there is a large gap in basic research concerning complexation of catecholamines by these compounds. Therefore, we decided to undertake studies on interaction of chosen catecholamines, namely: noradrenaline (norephinephrine), dopamine, L-DOPA, DOPA-P (phosphonic analog of L-DOPA) and catechol, with simple phenyl boronic acid PBA by means of potentiometry and NMR spectroscopy. For comparison, the binding properties of recently synthesized phenylboronic receptor 1 bearing aminophosphonate function in meta-position were investigated and showed promising ability to bind catecholamines. The protonation and stability constants of PBA and receptor 1 complexes were examined by potentiometry. The obtained results demonstrated that PBA binds the catecholamines with the following affinity order: noradrenaline⩾dopamine≈L-DOPA>catechol>DOPA-P, while its modified analog 1 reveals slightly different preferences: dopamine>noradrenaline>catechol>L-DOPA>DOPA-P. [Copyright &y& Elsevier]

Abstract: From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Eu3+(aq)+3A−(aq)+ 1 (nb) 1·Eu3+(nb)+3A−(nb) taking place in the two-phase water–nitrobenzene system (; 1 =macrocyclic lactam receptor – see Scheme 1; aq=aqueous phase, nb=nitrobenzene phase) was evaluated as log K ex (1·Eu3+, 3A−)=−4.1±0.1. Further, the stability constant of the 1·Eu3+ cationic complex in nitrobenzene saturated with water was calculated for a temperature of 25°C: log β nb (1·Eu3+)=9.0±0.1. Finally, by using DFT calculations, the most probable structure of the cationic complex species 1·Eu3+ was derived. In the resulting 1·Eu3+ complex, the “central” cation Eu3+ is bound by five bond interactions to two ethereal oxygen atoms and two carbonyl oxygens, as well as to one carbon atom of the corresponding benzene ring of the parent macrocyclic lactam receptor 1 via cation–π interaction. [Copyright &y& Elsevier]

Abstract: Polymer films of poly(vinylalcohol) (PVA) complexed with poly(ethyleneglycol) (PEG) with different dopant concentrations of Cu2+ ions are prepared by solution casting technique. Improvement in the crystallinity of the samples is observed with the X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis. Thermal transition and thermal degradation of the films with respect to copper concentration were studied by Differential Scanning Calorimetry (DSC) and thermo gravimetric analysis (TGA). The change in glass transition temperature (Tg) as a function of copper concentrations (x =1–5mol%) has been attributed to branching and steric effects in PVA+PEG complexes. In TGA curves low thermal degradation in the samples has been observed with high copper content. The EPR spectra of all the polymer samples exhibit resonance signals characteristic of Cu2+ ions. The spin-Hamiltonian parameter, indicate that the ground state of Cu2+ ions is and the site symmetry around Cu2+ ions is tetragonally distorted octahedral site. The spin concentration (N) participating in the resonance is measured as a function of temperature and it obeys Boltzmans law. The paramagnetic susceptibility (χ) is calculated from the EPR data at various temperatures and the Curie constant (C) is evaluated. The optical absorption spectrum exhibits a broad band at 784nm which is assigned to the 2 B 1 g → 2 B 2 g transition. [Copyright &y& Elsevier]

Abstract: The complexation of dimeric rhodium(II) tetrakistrifluoroacetylate with 25 ligands containing oxygen atoms: alcohols, ethers, ketones, aldehydes, carboxylic acids and esters in chloroform solution have been investigated by 1H and 13CNMR spectroscopy and Density Functional Theory (DFT) methods. Investigated ligands form 1:1 adducts in our experimental conditions, with stability constants in the order of several hundred mol−1. The exchange of ligands in solution is fast on the NMR spectroscopic timescale. The decrease of longitudinal relaxation times T 1 in ligands in the presence of rhodium salt has been tested as the means of determination of the complexation site in ligands. The influence of complexation on chemical shifts in ligands was evaluated by a parameter complexation shift Δδ (Δδ = δadd − δlig ). These parameters were positive (>0ppm) and did not exceed 1ppm for 1H NMR; and varied from ca. −5 to +15ppm in the case of 13CNMR. The calculation by DFT methods using the B3LYP functional (structure optimization, electronic energy) and B3PW91 functional (shielding), and combinations of the (6-31G(2d), 6-311G++(2d,p), and LANL2DZ basis sets, followed by scaling procedures reproduced satisfactorily 1H and 13C chemical shifts and, with some limitations, allowed to estimate Δδ parameters. [Copyright &y& Elsevier]

• The proposed method determined the Fe2+ and Fe3+ simultaneously with acceptable accuracy. • Chemometrics method OSC-PCR was used for deconvolution of the fluorescence spectral data. • The complexation reaction was studied, and the stability constants were calculated. • Ligand DALD act as a turn-off fluorescence probe for iron ions. In this research, a newly reported fluorescence molecular probe [N, N'-bis(methylsalicylaldehyde)-4,4 bipyridinium] dichloride (DALD) was used for selective detection and determination of Fe2+ and Fe3+ in aqueous solutions. The complexation reaction between DALD and Fe2+ and Fe3+ is the basis of the variation in the emission intensity and their quantitative fluorescence determination. The stoichiometries and formation constants of DALD and both ions were obtained by appropriate chemical model and numerical refinement of spectrofluorometric-mole ratio titration data. The selectivity of the probe towards Fe2+ and Fe3+ was tested in the presence of Mn+ (n = 1, 2, 3) cations. None of the other ions show any observable fluorescence signal quenching at the excitation and emission wavelengths (345/456 nm). The emission profile of said iron species was in the range of 340–560 nm and has shown a high degree of overlap. The univariate calibration ranges and detection limits of Fe2+ and Fe3+ were 0.7–4.1 μM, 0.7–2.7 μM and 1.3 μM, and 0.69 μM, respectively. The orthogonal signal correction-principal component regression (OSC-PCR) as a factor-based and data compression method was used to determine both cations in aqueous solutions simultaneously. OSC-PCR correlates the fluorescence spectra to the concentration of metal ions very well, and the coefficients of determination were 0.9530 and 0.9919 for Fe2+ and Fe3+, respectively. The solution equilibria of interaction between the probe and metal ions were studied and the stability constants of complexes were 10.68 (± 0.05), 1:2 and 4.46 (± 0.12) 1:1 for Fe2+ and Fe3+ respectively. The factors that influenced sensitivity and selectivity were recognized and optimized. [ABSTRACT FROM AUTHOR]

Three QSAR models were developed from the calculated molecular descriptors of coumarins and sulfocoumarin and their inhibitory activities (pK i s) measured towards one (namely CA XII) of the isoforms of Carbonic Anhydrase (CA). An additional, one more selective QSAR model was also developed in which selective inhibitory activity of the compounds was defined as differences of inhibition constants between CA XII and CA II isoforms. The first one, the global model comprises 40/15 training/test compounds with the statistical parameters of R2 = 0.797, Q2 = 0.702, s2 = 0.357, F = 26.796, R p r e. 2 = 0.783 and SE = 0.904. The second one, the coumarin model comprises 28/10 training/test compounds with the statistical parameters of R2 = 0.742, Q2 = 0.651, s2 = 0.417, F = 16.586, R p r e. 2 = 0.887 and SE = 0.968. The third model, the sulfocoumarin model comprises 15/2 training/test compounds with the statistics of R2 = 0.792, Q2 = 0.730, s2 = 0.289, F = 22.669, R p r e. 2 = 0.999 and SE = 0.353. The final model, the selective model consists of 21/5 training/test compounds with the statistical parameters of R2 = 0.806, Q2 = 0.693, s2 = 0.683, F = 23.670, R p r e. 2 = 0.886 and SE = 0.353. Interpretation of descriptors, HOMO-1 and LUMO energies in the models let us to hypothesize that hydrolyzed coumarins and sulfocoumarins are electrostatically bound to the enzyme, thus they presumably play critical roles at the beginning e.g. in the hydrolyzing reaction step of the ligands which affects the overall binding free energy of the ligand-isozyme complex. Image 1 • HOMO-1 of coumarins is an important factor for the binding selectivity towards CAs. • Hydrolyzing steps of coumarins play critical roles at the complexation reactions. • Isodensity surface descriptors are most significant ones for QSARs of the coumarins. [ABSTRACT FROM AUTHOR]