Single-crystal X-ray Structure Research Articles

Characterization of the O-centered vanadium selenoiodides V4OSe8I6·X (X = I2, 3,5-dimethylpyrazole)

O-centered vanadium(IV) selenoiodide V4OSe8I6·3,5-dimethylpyrazole was synthesized in a sealed glass ampoule at moderate temperature 220 °C from the mixture of V, Se, I2, small quantity of water and 3,5-dimethylpyrazole. The X-ray single crystal structure of the compound was solved. The crystal structure includes O-centered tetranuclear complex [V4(μ4-O)(μ-Se2)4(μ-I)2I4] in which vanadium atoms are bridged by diselenide (Se2)2– and iodide I– groups; four terminal iodides coordinate vanadium atoms additionally. Molecules of 3,5-dimethylpyrazole form non-covalent contacts with iodine and selenium atoms of the V4OSe8I6 complexes. Once compounds V4OSe8I6·3,5-dimethylpyrazole and V4OSe8I6·I2 contain similar electroneutral coordination molecular fragment V4OSe8I6, we present here a discussion of spectroscopic properties as well as thermal behavior. Comparing XPS data, both compounds contain vanadium complexes with major V 2p binding energies very similar to each other, and almost equal binding energies in XPS Se 3d and I 3d showing their forms of (Se2–)2 and I–, respectively. Thermolysis character of these compounds revealed higher stability of V4OSe8I6·I2 than V4OSe8I6·3,5-dimethylpyrazole, that indicates a greater stability of the system of non-covalent contacts involving iodine molecules than 3,5-dimethylpyrazole.

Unprecedented formation of azulicorroles from the scrambling of azulitripyrrane

In this study, we have prepared new tripyrranes embedded with azulene bearing two meso-pentafluorophenyl substituents. They were obtained as diastereomers in high yield which were separated using conventional column chromatography. Their distinct solution structures were unambiguously confirmed by NMR and mass analysis. Our synthetic strategy is simple and straightforward due to the reactivity of 1,3-positions of azulene, which underwent Lewis acid-catalyzed condensation with pyrrole-2-carbinol. These diastereomers were further subjected to acid-catalyzed (CF3COOH) condensation with pyrrole dicarbinol to afford the target N-confused azuliporphyrin (reduced form) in trace amount. However, we obtained the tris-meso-pentafluorophenyl substituted azulicorrole (AzCorA) as major product due to an unprecedented scrambling of the azulitripyrranes. The structural characterization of newly synthesized key precursors and macrocycles was done with the aid of high-resolution mass analyses, and 1H and 2D NMR analyses. The single crystal X-ray structure obtained for AzCorArevealed that the azulene subunit is tilted by 34.03[Formula: see text] due to the steric congestion of inner-NHs.

Synthesis, structure, thermal and magnetic properties of new tetranuclear copper(II) complex supported by multidentate ligand and glutarate functionality

A new tetranuclear Cu(II) complex, [Cu(H2O)4][Cu4(cpdp)2(glut)]Cl2·6H2O (1) was successfully constructed by utilization of carboxylate-based multidentate ligand N,N'-bis[2-carboxybenzomethyl]-N,N'-bis[2-pyridylmethyl]-1,3-diaminopropan-2-ol (H3cpdp), in combination with glutarate (glut) and Cu(II) ions, and characterized systematically. Originally, the symmetrical flexible ligand cpdp3− is capable to bind two Cu(II) ions, leaving behind accessible binding sites for further coordination of exogenous glutarate anion which facilitates the assembly of two ligand-bound Cu(II) pairs. In MeOH/H2O, the reaction of CuCl2·2H2O with H3cpdp and sodium glutarate in the presence of NaOH results in the formation of 1. Complex 1 was characterized by different analytical techniques, including single crystal X-ray structure investigation. Analysis of single crystal X-ray structure shows that 1 is a self-assembled tetranuclear copper complex in which two dinuclear [Cu2(cpdp)]+ species are exclusively bridged by one glutarate functionality through μ4:η1:η1:η1:η1 manner, acting as a coligand. Thermoanalytical methods (TGA/DTA) were used to examine the thermal stability and it was observed that 1 is stable up to ∼190°C. Variable temperature (2-300 K) magnetic susceptibility studies show the weak antiferromagnetic interactions among the copper centers with the value of magnetic exchange coupling constant (J) of -0.5 cm−1.

One pot synthesis of two potent Ag(I) complexes with quinoxaline ligand, X-ray structure, Hirshfeld analysis, antimicrobial, and antitumor investigations

In one pot, the self-assembly of AgNO3 and 2-chloroquinoxaline (2Cl-quinox) in water–ethanol mixture afforded two novel crystalline Ag(I) complexes. The major product is the polymeric complex [Ag(2Cl-quinox)(NO3)]n; (1), while the minor product (2) comprises two molecules which are the monomeric [Ag(2Cl-quinox)2(NO3)]; (2a) and polymeric [Ag(2Cl-quinox)(NO3)]n; (2b) complexes. The single crystal X-ray structure revealed that 1 and 2b are made up of two-dimensional infinite sheets. In contrast, 2a is a monomeric complex which has a highly distorted tetrahedral geometry around Ag(I) center. In all cases, the 2Cl-quinox molecule acts as a terminal monodentate ligand. Complexes 1 and 2b have similar molecular structures and also have almost similar crystal packing. Using Hirshfeld surface analysis, the O…H hydrogen bonds and π–π stacking interactions contributed significantly to the molecular packing. Both complexes have broad-spectrum action towards multi drug-resistance bacteria. The most effective function of 2 is against Proteus morganii, with a MIC value of 8 μg/mL. Complex 2 (IC50 = 5.93 ± 0.52 μg/mL) has remarkably greater cytotoxic effect against lung carcinoma (A-549) than cis-platin (IC50 = 7.5 ± 0.69 μg/mL) and AgNO3 (IC50 = 14.7 ± 0.53 μg/mL). The higher Ag-content in 2 could be the main reason for its higher cytotoxicity than 1.

Phenanthroline-based ligand scaffold as an efficient colorimetric and ratiometric fluorescence probe for Zn2+ and Cd2+ ion detection

A colorimetric and ratiometric fluorescent probe 2-(naphthalen-2-yl)-2,11b-dihydro-1H-imidazo[4,5-f][1,10]phenanthroline (probe 1), was designed and synthesized for sensitive and selective detection of Zn2+ and Cd2+ in methanol, test paper and actual water samples. When probe 1 was excited at 350 nm in methanol solution, in the presence of alkali metal ions, alkali-earth metal ions and a variety of transition metal ions, it showed sensitive fluorescence selectivity to Zn2+ and Cd2+. With the addition of Zn2+, the color of the solution changed from purple to green with the naked eye, and with the addition of Cd2+, the color of the solution changed from purple to cyan. The fluorescence intensity of probe 1 showed a good linear relationship with Zn2+ and Cd2+ concentrations, and the detection limits were 0.09 μM and 0.06 μM, respectively. The binding mode of probe 1 and Zn2+ was discussed according to the 1-Zn single X-ray crystal structure. In addition, the results of strip test and real water sample test showed that probe 1 has potential application in environmental metal ion recognition and detection.

Synthesis, characterization and cytotoxicity of copper (II) complex containing a 2H-benzo[e][1,3]oxazin derivative

A new cis-dihalo copper(II) complex, [CuII(HLbz)(Cl)2].CH3CN (1), where HLbz = (S)-2-(((2-(2-(pyridin-2-yl)-2H-benzo[e][1,3]oxazin-3(4H)-yl)ethyl)amino)methyl)phenol), was isolated by reacting copper(II) chloride dihydrate and the H2L ligand (H2L = 2,2′-((2-(pyridin-2-yl)imidazolidine-1,3-diyl)bis(methylene))diphenol) in a MeOH/CH3CN (1:3 v/v) mixture. The complex formation occurred via the ligand modification during complexation, producing a unique structure containing 2H-benzo[e][1,3]oxazin, as observed from the single crystal X-ray structure determination. The complex was characterized by elemental analysis, potentiometric titration, spectroscopic techniques (UV–Vis, FT-IR) and conductance measurements. Complex 1 inhibits the growth of myelogenous leukemia cells with an IC50 of 17.3 μmol L−1.

Synthesis, crystal structure and biological properties of a fluorophore-labelled mixed-ligand copper(II) complex incorporating N-hydroxynaphthalene-1,8-dicarboximide.

The mixed-ligand fluorophore-labelled copper(II) complex aqua[2,4-dioxo-3-azatricyclo[7.3.1.05,13]trideca-1(12),5,7,9(13),10-pentaen-3-olato-κ2O2,O3](1,10-phenanthroline-κ2N,N')copper(II) nitrate, [Cu(C12H6NO3)(C12H8N2)(H2O)]NO3·CH3OH or [Cu(L)(phen)(H2O)]NO3·CH3OH (where phen is 1,10-phenanthroline and HL is N-hydroxynaphthalene-1,8-dicarboximide), (1), was synthesized and structurally characterized. The structure of (1) was confirmed by single-crystal X-ray structure determination. The complex crystallized in the triclinic space group P-1. The geometry around the copper centre is distorted square pyramidal, with the apical position occupied by a water molecule. The complex is highly fluorescent in organic and aqueous solutions. It has good anticancer activity, with an IC50 value of 17 µM, which is almost five times greater than cisplatin (IC50= 82 µM) under identical experimental conditions.

Open-Cage Fullerene as Molecular Container for F- , Cl- , Br- and I.

A 19-membered open-cage fullerene derivative was prepared from C60 in 7 steps and 5.5 % yield through the peroxide-mediate pathway. There are four carbonyl groups, an ether oxygen and a quinoxaline moiety on the rim of the orifice. A chloride anion could be inserted into its cavity by heating with hydrochloric acid at 60 °C for 4 h. Encapsulation of fluoride, bromide and iodide anions was also achieved at slightly more forcing conditions, 90 °C for 14 h. Single crystal X-ray structures of the sodium salt of the chloride and the bromide encapsulated derivatives were obtained, which showed the halide anion in the center of the cavity and two sodium cations connecting two cages through coordination to the oxygen atoms on the rim of the orifices. The halide encapsulation ratio is quantitative in the isolated products.

Enzymatic Late-Stage Halogenation of Peptides.

The late-stage site-selective derivatisation of peptides has many potential applications in structure-activity relationship studies and postsynthetic modification or conjugation of bioactive compounds. The development of orthogonal methods for C-H functionalisation is crucial for such peptide derivatisation. Among them, biocatalytic methods are increasingly attracting attention. Tryptophan halogenases emerged as valuable catalysts to functionalise tryptophan (Trp), while direct enzyme-catalysed halogenation of synthetic peptides is yet unprecedented. Here, it is reported that the Trp 6-halogenase Thal accepts a wide range of amides and peptides containing a Trp moiety. Increasing the sequence length and reaction optimisation made bromination of pentapeptides feasible with good turnovers and a broad sequence scope, while regioselectivity turned out to be sequence dependent. Comparison of X-ray single crystal structures of Thal in complex with d-Trp and a dipeptide revealed a significantly altered binding mode for the peptide. The viability of this bioorthogonal approach was exemplified by halogenation of a cyclic RGD peptide.

Blue fluorescent Zinc(II) complexes bearing schiff base ligand for solution-processed organic light-emitting diodes with CIEy ≤ 0.09

Inspired by the blue fluorescent feature of metal schiff-base complexes, we have been successfully synthesized the blue fluorescent Zn(II) complexes (Zn-1 and Zn-2) bearing pyrazolone based azomethine ligands. The photophysical and electrochemical properties of these complexes have been investigated by several techniques in detail. Both complexes showed the emission in blue region and exhibited a good thermal stability. The single crystal X-ray structure analysis were performed to explicate their coordination adjustment around the Zn(II) metal ion. DFT and TDDFT methods performed to understand the involvement of metal ions and Schiff base ligand in the formation of frontier orbitals. For application in organic light emitting diodes, electroluminescent devices were fabricated by using simple solution-processed fabrication method. The best performance was observed at a low turn-on voltage of 3.5 V with a maximum external quantum efficacy of 3.2% for a deep-blue emission at a CIEy of 0.09.

A crystalline and stable microporous framework based on the dative B←N bonds

<h2>Summary</h2> The concept of making use of dative boron–nitrogen (B←N) bonds for the construction of microporous crystalline organic framework (BNF) materials has been proposed but not fulfilled, and they have not been fully explored for their diverse functions because of the difficulty to stabilize their pore structures under thermal/vacuum activation. In this study, we report the first such stable crystalline framework in which the single-crystal X-ray structures of the as-synthesized BNF-1, activated BNF-1a, and C₂H₂-loaded BNF-1a have been clearly characterized. Here, the 2D framework sheets of BNF-1 were interlocked with one another, generating the stable and crystalline framework with a Brunauer-Emmett-Teller (BET) surface area of 255 m²/g. Also, the material takes up more C₂H₂ than CO₂ molecules, and breakthrough experiments demonstrate its separation performance for C₂H₂/CO₂ mixtures. The molecular recognition mechanism of this BNF-1 for the preferential binding of C₂H₂ molecules over CO₂ has been comprehensively studied by both single-crystal X-ray diffraction and molecular modeling.

Synthesis, Molecular and Supramolecular Structures of Symmetric Dinuclear Cd(II) Azido Complex with bis-Pyrazolyl s-Triazine Pincer Ligand

A new dinuclear Cd(II)-azido complex of 2,4-bis(3,5-dimethyl-1H-pyrazol-1-yl)-6-methoxy-1,3,5-triazine (PMT) pincer ligand is synthesized. Its single crystal X-ray structure reveals the dinuclear [Cd(PMT)(Cl)(N3)]2 formula. The triclinic crystal parameters are a = 9.323(4) Å, b = 10.936(5) Å, c = 11.312(6) Å, α = 112.637(10)°, β = 104.547(11)° and γ = 105.133(10)° while V = 944.1(8) Å3. Due to symmetry considerations, the asymmetric unit comprises a half [Cd(PMT)(Cl)(N3)]2 formula. The Cd(II) is hexa-coordinated with one tridentate PMT ligand in a pincer fashion mode in addition to one terminal chloride and two azide ions bridging the two Cd(II) centers in double μ(1,1) bridging mode. Unusually, the Cd-N(s-triazine) bond is not the shortest among the Cd-N interactions with the PMT pincer ligand. The supramolecular structure of the dinuclear [Cd(PMT)(Cl)(N3)]2 formula is controlled by a significant amount of Cl…H (16.4%), N…H (25.3%), H…C (9.8%) and H…H (37.2%) interactions based on Hirshfeld surface analysis. Careful inspection of the shape index map reveals the presence of some weak π-π stacking interactions between the s-triazine and pyrazolyl moieties. The percentage of C…C contacts is 1.9% where the C2…C8 (3.462 Å) is the shortest while the centroid–centroid distance is 3.686 Å. Natural charge analysis describes the charge transferences from the ligand groups to the Cd(II), while and atoms in molecules (AIM) give an indication on the properties of the Cd-N and Cd-Cl bonds.

A Combined Experimental and Theoretical Investigation of Oxidation Catalysis by cis-[VIV(O)(Cl/F)(N4)]+ Species Mimicking the Active Center of Metal-Enzymes.

Reaction of VIVOCl2 with the nonplanar tetradentate N4 bis-quinoline ligands yielded four oxidovanadium(IV) compounds of the general formula cis-[VIV(O)(Cl)(N4)]Cl. Sequential treatment of the two nonmethylated N4 oxidovanadium(IV) compounds with KF and NaClO4 resulted in the isolation of the species with the general formula cis-[VIV(O)(F)(N4)]ClO4. In marked contrast, the methylated N4 oxidovanadium(IV) derivatives are inert toward KF reaction due to steric hindrance, as evidenced by EPR and theoretical calculations. The oxidovanadium(IV) compounds were characterized by single-crystal X-ray structure analysis, cw EPR spectroscopy, and magnetic susceptibility. The crystallographic characterization showed that the vanadium compounds have a highly distorted octahedral coordination environment and the d(VIV-F) = 1.834(1) Å is the shortest to be reported for (oxido)(fluorido)vanadium(IV) compounds. The experimental EPR parameters of the VIVO2+ species deviate from the ones calculated by the empirical additivity relationship and can be attributed to the axial donor atom trans to the oxido group and the distorted VIV coordination environment. The vanadium compounds act as catalysts toward alkane oxidation by aqueous H2O2 with moderate ΤΟΝ up to 293 and product yields of up to 29% (based on alkane); the vanadium(IV) is oxidized to vanadium(V), and the ligands remain bound to the vanadium atom during the catalysis, as determined by 51V and 1H NMR spectroscopies. The cw X-band EPR studies proved that the mechanism of the catalytic reaction is through hydroxyl radicals. The chloride substitution reaction in the cis-[VIV(O)(Cl)(N4)]+ species by fluoride and the mechanism of the alkane oxidation were studied by DFT calculations.

Trapping of a Late-Metal Terminal Sulfido Intermediate with Phenyl Isothiocyanate

Nickel–sulfur bonds play key roles in catalysis and biological systems. In most metal complexes, sulfur acts as a bridge joining metal centers, rather than as a terminal sulfide ligand. The addition of phenyl isothiocyanate to Ni(dcpe)(Ph)(SH) afforded the dithiocarbamate complex Ni(dcpe)(κ2-S2C═NPh) with the loss of benzene. The reaction was monitored by UV–visible spectroscopy under pseudo-first-order rate conditions and showed limited dependence on isothiocyanate concentration, suggesting that the reaction proceeds through an intermediate terminal sulfido nickel complex. The values of ΔH⧧ and ΔS⧧ for the reaction were found to be 18.6 ± 1.5 kcal/mol and −17.8 ± 4.7 eu, respectively. Full characterization of Ni(dcpe)(κ2-S2C═NPh), including a single-crystal X-ray structure determination, was achieved.

Crystal structure of a heterotrimetallic 12-metallacrown-4 with 2-propylvalerate anion bridges

The synthesis and single-crystal X-ray structure for tetraaquatetrakis(μ-2-propylvalerato)tetrakis(μ4-salicylhydroximato)dysprosiumtetramanganesesodium dimethylformamide tetrasolvate, [DyMn4Na(C7H4NO3)4(C8H15O2)4(H2O)4]·4C3H7NO or DyNa(2-PV)4[12-MCMnIII Nshi-4](H2O)4·4DMF, 1, where MC is metallacrown, shi3− is salicylhydroximate, 2-PV is 2-propylvalerate, and DMF is N,N-dimethylformamide, is reported. The slightly domed metallamacrocycle contains four ring MnIII ions and four shi3− ligands that generate an [MnIII—N—O] repeat unit that recurs four times. The ring MnIII ions are five-coordinate with a square-pyramidal shape. Furthermore, the metallacrown binds both a DyIII ion and a Na+ ion in the central cavity. The central ions are located on opposite faces of the cavity with the DyIII ion located on the convex side of the MC and the Na+ ion located on the concave side. Each central ion is eight-coordinate although they possess different geometries. The DyIII ion has a square-antiprismatic shape, while the Na+ ion has an extremely distorted biaugmented trigonal–prismatic shape. The four 2-propylvalerate anions help to tether the DyIII to the MC cavity by forming bridges between the DyIII ion and each ring MnIII ion. Moreover, the interstitial DMF molecules are hydrogen bonded to the water molecules that complete the coordination environment of the Na+ ion. The metallacrown framework (excluding the DyIII and Na+ ions), the bridging 2-propylvalerate, and the interstitial DMF molecule experience whole-molecule disorder due to the rotational orientation of the metallamacrocycle. Additionally, the main moiety alkyl chain of the 2-propylvalerate is disordered over two additional orientations, and the main moiety interstitial DMF molecule is disordered over one additional orientation. The main moiety of the metallacrown framework refined to 0.9030 (14), while the minor B-moiety refined to 0.0971 (14). The main moiety alkyl chain of the 2-propylvalerate refined to 0.287 (3): 0.309 (3): 0.307 (3), and the minor B-moiety alkyl chain refined to 0.0971 (14). Lastly, the main moiety interstitial DMF refined to 0.549 (3): 0.354 (3), and the minor B-moiety DMF refined to 0.0971 (14).

Selective Turn-On Fluorescence Sensing of Cyanide Using the Pyridoxal Platform of a Ni(II) Complex

Cyanide is a very toxic pollutant to aquatic life and the environment. Analytical methods for the quantitative assay of cyanide, which are rapid, sensitive (low limit of detection), and cost-effective, are in great demand. Colorimetric and fluorometric methods are ideally suited for this purpose. In this report, we describe a Ni(II) complex containing a pyridoxal platform for the rapid and sensitive fluorometric estimation of cyanide. The square-planar Ni(II) complex, [Ni(L)(N3)]·3H2O, where the ligand LH = 4-[(2-dimethylamino-ethylimino)-methyl]-5-hydroxymtheyl-2-methyl-pyridin-3-ol, a Schiff base formed between pyridoxal and (2-dimethylamino)ethyl amine, was synthesized and characterized by various spectroscopic techniques as well as by single-crystal X-ray structure determination. The complex was found to selectively bind CN- in the presence of other biologically important anions such as F-, Cl-, Br-, I-, OAc-, S2-, NO3 -, PO4 3-, SO4 2-, and H2PO4 - in tris-HCl/NaCl buffer [pH = 7.4], and it can be monitored by fluorescence turn-on or by UV-visible spectroscopy. The binding constant of the complex with CN- was estimated to be 2.046 × 1014 M-2 and the limit of detection (LOD) was 9 nM, the LOD being considerably lower than the maximum permissible level of cyanide ions (1.9 μM) in drinking water, as recognized by the World Health Organization (WHO). The effects of pH and temperature on the sensing are also investigated. The Ni(II) complex is also found to bind to calf-thymus DNA very strongly, and the apparent binding constant (K app) was determined to be 1.33 × 107 M-1 by the fluorescence quenching of the ethidium bromide-DNA adduct by the complex.

Spectroscopic, structural and computational studies of thiophenolato bridged dirhenium(III,III) complexes

Thiophenol (HLH), 4-methylthiophenol (HLMe) and 4-chlorothiophenol (HLCl) react with dirhenium(III,II) complex [Re2(µ-O2CCH3)Cl4(µ-dppm)2] (1) (dppm = Ph2PCH2PPh2) in refluxing dry toluene to afford the diamagnetic Re2 6+ complexes of the type [Re2(μ-LR)2Cl4(μ-dppm)2] (2(LR)) [LR = C6H5S–, p-MeC6H4S– and p-ClC6H4S–]. These are the first examples of thiophenolato bridged dirhenium complexes with a Re2 6+ core containing dppm ligand. The spectral properties of the complexes are reported. In the electrochemical experiment, the type 2(LR) complexes show one quasi-reversible one-electron oxidation and one-electron reduction waves. The identity of 2(LMe) has been established by single-crystal X-ray structure determination (Re–Re distance = 2.6178(5) Å) and is shown to have an edge-shared bi-octahedral structure. DFT analysis shows that the highest occupied molecular orbitals are mainly composed of metal δ-based orbitals whereas the lowest unoccupied molecular orbitals are metal π*-based orbitals and the electronic ground state for the 2(LR) complexes is σ2π2δ*2δ2. Time-dependent DFT (TD-DFT) analysis shows that the sharp peak at 455 nm in the experimental UV-vis spectrum is mainly due to the [Cl(π)]→[Re2(π*)] transition.

Synthesis, Structure, and Optical Properties of a Bis-Macrocycle Derived from a Highly Emissive 1,3,6,8-Tetra(1H-pyrrol-2-yl)pyrene.

A tetra-functionalized pyrene precursor 4b is prepared using the Suzuki-Miyaura coupling of 1,3,6,8-tetrabromopyrene with N-Boc-2-pyrroleboronic acid. 4b displayed a blue emission with a high quantum yield (ϕF = 0.89). 4b is subjected to [3 + 2] Lewis acid-catalyzed condensation with 2,2'-bithiophene-dialcohol 5, affording a planar bis-N2S2 internally linked with pyrene. The single-crystal X-ray structure of bis-N2S2 revealed a planar conformation with all of the pyrrolic nitrogens and thiophenic sulfurs pointing toward the macrocyclic core. Further, the reduction of bis-N2S2 was attempted in the presence of Zn/NH4Cl at room temperature in CHCl3. A sharp color change from pink to brown was observed presumably due to the formation of its reduced congener bis-N2S2-2H. However, the reduced species was found to revert back to its oxidized form over a period of 25 min in CHCl3. Density functional theory (DFT) studies reveal that the two monocyclic halves of bis-N2S2-2H exhibit differences in aromaticity depending on amino and imino pyrroles present inside each individual core. Such a conversion was also monitored by ultraviolet-visible (UV-vis) absorption spectral studies, and the exact composition of bis-N2S2-2H was confirmed by High-resolution/mass spectrometry (HR/MS) analysis. Experimental and theoretical studies reveal a weak aromatic character of bis-N2S2 due to the absence of global conjugation.

Crystal Structures of Half-Sandwich Ru(II) Complexes, [(η6-p-Cymene)(3-chloro-6-(1H-pyrazol-1-yl)pyridazine)Ru(X)]BF4, (X = Cl, Br, I)

Herein, we report the synthesis and single-crystal X-ray structures of three (η6-p-cymene)Ru(II) tetrafluoroborate salts, viz., [(η6-p-cymene)(3-chloro-6-(1H-pyrazol-1-yl)pyridazine)Ru(X)]BF4, (X = Cl, Br, I), Ru1-3. They were prepared by the reactions of [(η6-p-cymene)Ru(μ-X)(X)]2, (X = Cl, Br, I) with two-mole equivalents of 3-chloro-6-(1H-pyrazol-1-yl)pyridazine, under inert conditions at ambient temperatures, and subsequently precipitated by the addition of excess BF4− ions. Orange crystalline precipitates were obtained in good yields, from which the respective single crystals for X-ray diffraction analysis were recrystallized by slow evaporation from their methanolic/diethyl ether solutions. The Ru(II) complexes were characterized by various spectroscopic techniques and chemical methods, which included FTIR, 1H/13C NMR, UV-visible absorption, mass spectrometry, and elemental analysis. The molecular structures were solved by single-crystal X-ray crystal diffraction analysis. The complexes crystallized in the monoclinic crystal system in the P21/c (Ru1-2) and P21/n (Ru3) space groups. Density Functionals Theoretical (DFT) calculations were performed in methanol to gain an understanding of the electronic and structural properties of the complexes. Trends in the data metrics were established, and selected data were compared with the diffraction data. The electrophilicity indices of Ru1-3 follow the order Ru3 &gt; Ru2 &gt; Ru1, and the trend is in line with their anticipated order of reactivity towards nucleophiles.

Structural, DFT calculations and photophysical and photochemical characteristics of 1-((E)-2-phenylethenyl)-2-(4-(2-((E)-2-phenylethenyl) phenoxy) butoxy) benzene (PPPBB)

X-ray single crystal structure and spectroscopic and photophysical parameters of the titled compound were studied. The titled compound shows thermal stability prior to melting at 126.17 °C with Δ H value of 109.991 J g−1. Photophysical parameters include singlet electronic absorption, molar absorption coefficient, oscillator strength, and dipole moment of electronic transition, fluorescence spectra, excited state lifetime, and fluorescence quantum yield for 1-((E)-2-phenylethenyl)-2-(4-(2-((E)-2-phenylethenyl) phenoxy) butoxy) (PPPBB) in different solvents. PPPBB displays a little change in maximum absorption and emission spectra with solvent polarity, indicating a slight change in dipole moment of dye molecules upon excitation. The dipole moments' (Δ μ) difference between the excited and ground states was obtained from the Lippert–Mataga method. Ground and electronic excited states' geometric optimization was performed using density functional theory (DFT) and time-dependent density functional theory (time dependent-DFT), complemented with spectral findings. A good agreement between theoretical data and experimental observations was found. The net photochemical quantum yield (φc) of PPPBB dye was calculated in various solvents.