Pyrazolyl Ring Research Articles

Coordination chemistry of 4-aminopyrazole: Structure and physicochemical properties of cobalt(II) chlorido complexes, and amino group reactivity towards a ketone to yield an imine bond

An outline of the in situ construction of a coordination polymer by reacting a mononuclear cobalt(II) complex, functionalised with an amine substituent, with acetone is given. The methodology involved 4-amino-3,5-diisopropyl-1-pyrazole (denoted as L1pzHNH2) as the precursor, putative linker molecule. Reaction of the ligand with anhydrous cobalt(II) chloride, yielded a four-coordinated cobalt(II) chlorido complex, [CoCl2(L1pzHNH2)2]. When the complex was reacted with acetone, a four-coordinated cobalt(II) chlorido coordination polymer, [CoCl2{L1pzHN=C(CH3)2}]n, with an imine bond, was obtained. The complexes were characterised by various spectroscopic techniques. X-ray crystallography shows [CoCl2(L1pzHNH2)2]·2(thf) to comprise a tetrahedrally coordinated cobalt(II) centre with the donors being two chlorido and two pyrazolyl-N atoms. Similarly, [CoCl2{L1pzHN=C(CH3)2}]n features a Cl2N2 donor set defining an approximately tetrahedral geometry with the imine-N donors being derived from a pyrazolyl ring and a symmetry related exocyclic imine-N atom with the result that a one-dimensional coordination polymer with a helical topology is formed. When the uncoordinated precursor molecule, L1pzHNH2, was reacted with acetone, the formation of the imine was confirmed by 1H NMR measured in (CD3)2CO solution. However, from the 1H NMR measured for the imine in CDCl3 solution, a 70:30 equilibrium between the imine and amine was established. It is concluded that the nucleophilicity of the amine group is enhanced by the binding of cobalt(II) to the pyrazole nitrogen in [CoCl2(L1pzHNH2)2]·2(thf), thereby favouring irreversible imine formation. The facile formation of [CoCl2{L1pzHN=C(CH3)2}]n in the solid-state also correlates with the reduced solubility of the coordination polymer structure in organic solvents.

Anticancer, antimicrobial and photocatalytic activities of a new pyrazole containing thiosemicarbazone ligand and its Co(III) and Ni(II) complexes: Synthesis, spectroscopic characterization and X-ray crystallography

A new pyrazole based thiosemicarbazone ligand, 5-methyl-3-formylpyrazole-N(4)-isopropylthiosemicarbazone, (HMPzNHPri) (compound I), and its cobalt(III) and nickel(II) complexes, [Co(MPzNHPri)2]Cl (compound II) and [Ni(HMPzNHPri)2]Br2 (compound III), respectively, have been synthesized and characterized through various physico-chemical and spectroscopic studies. Both the reported Co(III) and Ni(II) complexes are cationic in nature and behave as 1:1 and 1:2 electrolytes in MeOH, respectively. Electronic spectral features of the complexes have classified them as distorted octahedral ones. IR spectral data (4000–450 cm−1) have suggested a monoprotic tridentate (NNS) function of compound I coordinating to the Co(III) ion via the pyrazolyl (tertiary) ring nitrogen, azomethine nitrogen and thiolato sulphur atom; while for compound III, compound I has been found to act as neutral NNS tridentate one, coordinating to Ni(II) via the pyrazolyl iminic nitrogen, azomethine nitrogen and thioketo sulphur. Structural features of all the compounds are confirmed by the single crystal X-ray data. All the compounds reported here have been found to exhibit significant photocatalytic activity towards degradation of Methylene Blue (MB) under UV radiation. Anticancer activity of all the three compounds against cancer cell lines (HeLa and A549) and a normal cell line (HEK293) have been investigated. Compound II has been found to be more efficient against the human cervical cancer cell (HeLa) and the lung cancer cell (A549) than compounds I and III. The ligand and both the complexes display potential activities against both gram-positive (Bacillus subtilis MTCC 7193) and gram-negative bacteria (E. coli MTCC 1610).

An structural study of nine-membered monometallocycles of Pd(II) and Pt(II) employing the 1,4-bis(3,5-dimethyl-1H-pyrazol-1-yl)butane ligand

Two nine-membered metallocycles of PdII (1) and PtII (2) containing 1,4-bis(3,5-dimethyl-1H-pyrazol-1-yl)butane ligand (L1) have been prepared and their structures were determined by IR, NMR spectroscopy, and by single-crystal X-ray diffraction analysis. The molecular structures of L1 display that the pyrazolyl groups adopt an anti-conformation, while in 1 and 2 a discrete nine-membered monometallic macrocycle is generated by the assembly of one ligand and one metal atom, and the ring adopts a twist-chair-boat conformation. The ligand L1 in complexes 1 and 2 acts as cis-chelating ligand via a κ2 N,N coordination mode by the nitrogen atoms of the pyrazolyl rings. In compounds 1 and 2 the metal center adopts a planar geometry. The molecular structure of 1 and 2 also revealed two intramolecular anagostic interactions M•••Hγ–C(sp3) (M = Pd and Pt) with M•••H distances between 2.689 and 2.780 Å, which are important to stabilize the nine membered ring formed. Considering those two M•••Hγ interactions, the ligand L1 generates a κ4 N,N,H,H coordination mode and the metal centers adopt a trigonal prism geometry. The crystal packing of L1, 1 and 2 displayed supramolecular networks promoted mainly by C–H•••π interactions, which were analyzed by Hirshfeld Surface Analysis

Borotropy: The Mechanism of Boron Transfer Between Adjacent N‐Atoms of Pyrazol‐1‐yl Rings

AbstractThis work examines theoretically the problem of the migration of borane groups between the nitrogen atoms of pyrazolyl rings. We have studied as a model the BH2 pyrazol‐1‐yl derivatives to determine the effects of substituents on the pyrazole ring; also 1‐(9‐borabicyclo[3.3.1]nonan‐9‐yl)‐1H‐pyrazoles to compare the calculated barriers with the experimental ones as well as to determine steric effects, i. e., how the buttressing effect increases the rate. The interacting quantum atoms methodology has been used for partitioning the energy of the systems in their stationary points into the contribution of pyrazole and BH2 group and their mutual interaction.

Synthesis, characterization, photoluminescence properties, DFT studies, photocatalytic and antifungal activity of a new pyrazole-containing thiosemicarbazone ligand and its Co(III) and Ni(II) complexes

A new pyrazole-based thiosemicarbazone ligand, 5-methyl-3-formylpyrazole-N(4)-dipentylthiosemicarbazone (HMPzNPent2) (1), and its Co(III) and Ni(II) complexes, [Co(MPzNPent2)2]Br (2) and [Ni(HMPzNPent2)2]Cl2 (3), respectively, were synthesized and characterized. Complexes 2 and 3 are cationic in nature and behave as 1:1 and 1:2 electrolytes in MeOH, respectively. Electronic spectral features of the complexes indicate distorted octahedral structures. IR spectral data (4000–450 cm−1) suggest monoprotic tridentate (NNS) coordination of 1 to Co(III) via the pyrazolyl (tertiary) ring nitrogen, azomethine nitrogen and thiolato sulfur; In contrast, 1 is a neutral NNS tridentate donor in 3, coordinating to Ni(II) via the pyrazolyl iminic nitrogen, azomethine nitrogen and thioketo sulfur. Structural features of the compounds were confirmed by DFT calculations. TD-DFT absorption spectra authenticate that the simulated peaks are in reasonable agreement with the experimentally resolved peaks. Fluorescence spectral studies revealed photoluminescent behavior. The three compounds reported here have photocatalytic activity. 1 (used as positive control) and 3 show similar antifungal activity in inhibiting the growth of the phytopathogen Colletotrichum siamense (CS), whereas 2 is less efficient to control the growth of CS. Both 3 and 2 show antifungal activity against Colletotrichum gloeosporioides (AP2). Compound 3 is more effective to prevent the growth of phytopathogen Fusarium equisetum (F.E) than 2 and 1 (positive control).

Catalytic and anticancer activity of two new Ni(II) complexes with a pyrazole based heterocyclic Schiff-base ligand: Synthesis, spectroscopy and X-ray crystallography

A new pyrazole containing ‘NN’ bidentate Schiff-base ligand, N-(furan-2-ylmethyl)-1-(5-methyl-1H-pyrazol-3-yl)methanimine, (MPAFA) (compound I) and its two new Ni(II) complexes, [Ni(MPAFA)2(H2O)2].2Cl·2H2O (compound II) and [Ni(MPAFA)3].2ClO4 (compound III) have been synthesized and characterized by various physico-chemical and spectral parameters viz., elemental analyses, mass, IR, NMR (1H and 13C, ligand only), UV–vis spectral parameters and X-ray crystallographic studies. Both the complexes are behaving as 1:2 electrolytic species and the primary ligand, MPAFA, acts as a neutral ‘NN’ bidentate one in both the complexes. IR spectral data revealed that the coordination to each of the metal center in both II and III, takes place through the pyrazolyl (tertiary) ring nitrogen and the azomethine nitrogen atom. X-ray data have revealed that both II and III are octahedral in nature and confirmed a NiN4O2 and NiN6 octahedral coordination, respectively. Ni(II) ion has formed two sets of complexes; in II, two molecules of ligand and two water molecules are coordinated to the metal forming a mixed ligand complex (1:2 complex), while in III, three ligand molecules are coordinated to the metal (1:3 complex). The ligand and the Ni(II) complexes reported here have been tested for their catalytic and anticancer activities. II and III have been found to be efficient in reducing 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in presence of sodium borohydride (NaBH4) as a reducing agent; and are more potent cytotoxic agents and stronger anti-cancer materials against the breast cancer cell lines MCF7 and MDA-MB-231 than the primary ligand system.

Copper(II) and zinc(II) complexes bridged by benzenoid aromatic oxocarbon and dicarboxylate dianions

A novel series of Cu(II) and Zn(II) complexes were constructed through the bridging croconate (C5O5)2−, squarate (C4O4)2− and 2,5-pyridine-dicarboxylate (Py2,5-dc)2− dianions. These include pent- [Cu5(epdmpy)4(C5O5)2(H2O)6](ClO4)6‧12H2O (1) and tri-nuclear [Cu3(bepza)2(Py2,5-dc)2(ClO4)2(H2O)2]‧2H2O (4), dinuclear [Zn2(MeDPA)2(C4O4)(H2O)4](ClO4)2 (7), and 1-D- coordination polymers (CPs) catena-{[Cu2(bpzpy)2(C5O5)](ClO4)2‧MeOH} (2) and catena-{[Zn(4,4′-bipy)(H2O)4](C5O5)(H2O)} (6) as well as the mononuclear [Cu(HBph2,2′-dc)(pmdien)]ClO4 (5) have been synthesized and spectroscopically characterized as well as by single crystal X-ray crystallography. The reaction of aqueous solution Cu(ClO4)2, pymeea and C5O52− resulted in the unprecedently bis(oxalato) [Cu2(Pymeea)2(C2O4)(ClO4)2(H2O)2] (3). In these complexes, (C5O5)2−, squarate (C4O4)2− and (Py2,5-dc)2− ligands display a variety of coordination bonding modes. In complexes 1 and 2 the croconato is binding as 1,2-bidentate-3-monodentate but in addition 5-mono-dentate semi-coordinate bonding was detected for 2, whereas in 6 as counter dianion. The bonding mode in the squarato 7 was achieved through the trans μ1,3-mono-dentate. In the di-carboxylato compounds, only five-membered chelate ring was formed in 5via one of the carboxylate groups, whereas in 4 bridging was conducted through a mono-carboxylate and five-membered chelate ring including the second carboxylate and pyridyl nitrogen. In complexes 1–5 and 7, hydrogen bonds of type OH⋯O and/or NH⋯O are connecting the complex cations with the perchlorate anions/ligands to generate different dimensional supramolecular network structures, whereas in 6, the 3D network was formed through hydrogen bonding between the coordinated aqua and lattice water molecules. Non-covalent ring⋯ring interactions were also observed between pyridyl rings in complexes 1, 6 and 7, and between pyrazolyl rings as well as pyridyl ring in 2.

Laser spectroscopic characterization of supersonic jet cooled 2,7-diazaindole.

We report the first gas phase comprehensive study of the electronic spectroscopy of 2,7-diazaindole molecule in the ground and excited states. Single vibronic level fluorescence spectroscopy (SVLF) was performed to determine the ground state vibrations of the molecule, which depicted a large Franck-Condon activity beyond 2600 cm-1. For the excited state characterization, laser-induced fluorescence (LIF) and two-color resonant two-photon ionization spectroscopy (2C-R2PI) were performed. The band origin (000) for S1 ← S0 transition appeared at 33910 ± 1 cm-1 which was red shifted by 718 cm-1 and 1322 cm-1 compared to that of 7-azaindole and indole respectively. The Franck-Condon active vibrational modes in the spectra were seen till the (000) + 1600 cm-1 region. The IR-UV hole burning spectroscopy confirmed the absence of any other isomeric species in the molecular beam. The ionization energy (IE) of the molecule was measured as 8.921 ± 0.001 eV, recorded using photoionization efficiency spectroscopy. The above IE value was significantly higher than that of the related indole derivatives, suggesting the higher photostability of the 27DAI molecule due to N(2) insertion. The ground and excited state N-H stretching frequencies of the molecule were determined using fluorescence-dip infrared spectroscopy (FDIR) and resonant ion-dip infrared spectroscopy (IDIR), and the values are 3523 and 3467 cm-1, respectively. The lower value of νNH in the electronic excited state implied the increased photoacidity of the group. A comparative analysis of the experimental LIF/2C-R2PI spectra was done against Franck-Condon simulated spectra at three different levels of theory. The vibrational frequencies calculated at B3LYP-D4/def2-TZVPP showed the most accurate prediction in comparison with the experimentally detected symmetric modes in the ground state. However, in the excited state, the lower energy asymmetric modes simulated at the B3LYP/def-SVP level of theory provided the best agreement with the experiment. This is most probably due to the distortion observed at the pyrazolyl ring leading to the appearance of asymmetric vibrational modes. The above study highlights the possibility to appropriately tune the excitation wavelengths as well as alter the photostability of the organic chromophores via additional N-insertion in the molecular systems.

Spin‐Crossover Tuned Rotation of Pyrazolyl Rings in a 2D Iron(II) Complex towards Synergetic Magnetic and Dielectric Transitions

AbstractMaterials showing synergy of magnetic and dielectric transitions are promising candidates for future molecular devices. The challenge is how to realize synergy between spin and dielectric transitions with responses to external stimuli. Herein, we design a 2D spin crossover (SCO) complex, [FeII(dpa)][(pzTp)FeIII(CN)3]2 (1) (dpa=1,2‐bis(4‐pyridyl)ethyne and pzTp=tetrakis(pyrazolyl)borate). The local structural changes about the FeII ion were propagated to the whole crystal through the rigid bridging ligands (dpa), leading to elastic interactions to realize the abrupt SCO and rotational movements of polar apical pyrazolyl rings in the [(pzTp)FeIII(CN)3]− units. Dielectric measurements confirmed a substantial dielectric change (Δϵ′=2.3) upon the spin transition. This work provides a rational strategy to couple the spin transition and rotation of polar components, which is crucial for the synergetic switch of magnetism and dielectricity.

Spin-Crossover Tuned Rotation of Pyrazolyl Rings in a 2D Iron(II) Complex towards Synergetic Magnetic and Dielectric Transitions.

Materials showing synergy of magnetic and dielectric transitions are promising candidates for future molecular devices. The challenge is how to realize synergy between spin and dielectric transitions with responses to external stimuli. Herein, we design a 2D spin crossover (SCO) complex, [FeII (dpa)][(pzTp)FeIII (CN)3 ]2 (1) (dpa=1,2-bis(4-pyridyl)ethyne and pzTp=tetrakis(pyrazolyl)borate). The local structural changes about the FeII ion were propagated to the whole crystal through the rigid bridging ligands (dpa), leading to elastic interactions to realize the abrupt SCO and rotational movements of polar apical pyrazolyl rings in the [(pzTp)FeIII (CN)3 ]- units. Dielectric measurements confirmed a substantial dielectric change (Δϵ'=2.3) upon the spin transition. This work provides a rational strategy to couple the spin transition and rotation of polar components, which is crucial for the synergetic switch of magnetism and dielectricity.

Rational Design, Chemical Syntheses, and Biological Evaluations of Peripherally Selective Mu Opioid Receptor Ligands as Potential Opioid Induced Constipation Treatment.

Opioid-induced constipation (OIC) is a common adverse effect of opioid analgesics. Peripherally acting μ opioid receptor antagonists (PAMORAs) can be applied in the treatment of OIC without compromising the analgesic effects. NAP, a 6β-N-4-pyridyl-substituted naltrexamine derivative, was previously identified as a potent and selective MOR antagonist mainly acting peripherally but with some CNS effects. Herein, we introduced a highly polar aromatic moiety, for example, a pyrazolyl or imidazolyl ring to decrease CNS MPO scores in order to reduce passive BBB permeability. Four compounds 2, 5, 17, and 19, when administered orally, were able to increase intestinal motility during morphine-induced constipation in the carmine red dye assays. Among them, compound 19 (p.o.) improved GI tract motility by 75% while orally administered NAP and methylnaltrexone showed no significant effects at the same dose. Thus, this compound seemed a promising agent to be further developed as an oral treatment for OIC.

Chromium Complexes Supported by Phenyl Ether‐Pyrazolyl [N,O] Ligands as Catalysts for the Oligo‐ and Polymerization of Ethylene

A new series of Cr (III) complexes [Cr{1‐(3‐phenoxypropyl)‐1H‐pyrazole}Cl3]2 (Cr1), [Cr{1‐(3‐phenoxypropyl)‐3,5‐dimethyl‐1H‐pyrazole}Cl3]2 (Cr2), and [Cr{1‐(3‐phenoxypropyl)‐3‐phenyl‐1H‐pyrazole}Cl3]2 (Cr3) have been synthesized and characterized by elemental analysis, high‐resolution mass spectrometry (HRMS) and IR spectroscopy. Upon activation with methylaluminoxane (MAO), chromium precatalysts Cr2 and Cr3 showed moderate activity in ethylene oligomerization [TOF = 17,900–29,200 mol (ethylene)·mol (Cr)−1·h−1 at 80 °C] with Schultz‐Flory distribution of oligomers (K = 0.54–0.66) and production of polymer varying from 2.8 to 6.7 wt.%. On the other hand, under identical oligomerization conditions, Cr1/MAO behaved as a polymerization catalyst generating predominantly polyethylene (63.7 wt%). The amount of 1‐butene is the largest component in the liquid fraction suggesting that these precatalysts operate via a Cossee‐Arlman mechanism. The catalytic activities, selectivity and product distribution are quite sensitive to the R‐group at the 3‐ and 5‐position of the pyrazolyl ring. Based on the electronic and steric effects of R‐ substituents, it is possible to stablish a trend of activity: Cr2(PzMe2) > Cr3(PzPh) > Cr1(Pz). Moreover, the effect of oligomerization parameters (cocatalyst, temperature, [Al]/[Cr] molar ratio, time) on the activity and on the product distribution were examined.

2-[3-(4-Chloro-phen-yl)-5-(4-fluoro-phen-yl)-4,5-di-hydro-1H-pyrazol-1-yl]-5-[(4-fluoro-phen-yl)diazen-yl]-4-methyl-thia-zole.

The mol-ecule of the title compound, C25H18ClF2N5S, comprises almost co-planar fluoro-phenyl, methyl-thia-zolyl, pyrazolyl and chloro-phenyl rings with the second fluoro-phenyl ring almost perpendicular to this plane. One fluoro-phenyl group is disordered over two components of occupancy ratio 0.767 (10):0.233 (10) related by a 24.2 (8)° twist. In the crystal, two mol-ecules related by inversion symmetry are linked by a pair of C-H⋯F contacts in an R(8)2 2 geometry.

Tuning the catecholase activity of bis(pyrazolyl)methane-based copper(II) complexes by substitutions of the ligand core: unraveling a dual O2/H2O2 oxidation mechanism

Five new dinuclear copper(II) complexes based on dicompartmental ligands of the general formula R1R2R1-C6(OH)[C(O)-NH-CH2-CH(pz)2]2 (pz = pyrazolyl ring, R1 = R2 = H: HHH-Cu2; R1 = H, R2 = t-Bu: HButH-Cu2; R1 = Me, R2 = H: MeHMe-Cu2; R1 = Me, R2 = Br: MeBrMe-Cu2; R1 = Me, R2 = NO2: MeNO2Me-Cu2) were prepared and characterized in both solution and solid state. The phenoxide moiety acts as a bridge between two copper(II) centers; the remaining coordination sites of the metals are filled by the deprotonated N-amide atoms, the nitrogen atoms originating from the bis(pyrazolyl)methane groups and one exogenous hydroxide bridge. The catecholase-type activity of these dicopper complexes was studied in methanol, using a combination of aerobic and anaerobic methods. These investigations revealed that the substitution pattern of the central arene ring has an impact on the catalytic activity of our complexes, with the catalytic activity increasing in the following order: HHH-Cu2 <HButH-Cu2 <MeNO2Me-Cu2 <MeBrMe-Cu2 <MeHMe-Cu2. H2O2 was identified as the byproduct of O2 reduction. Its influence on the catalytic mechanism has been examined and found to have an impact on the catecholase-type reaction using these catalysts. Based on these findings, a dual mechanism for the catechol oxidation is proposed, where both molecular oxygen and the formed hydrogen peroxide act concurrently as oxidants.

Selective Isomer Formation and Crystallization-Directed Magnetic Behavior in Nitrogen-Confused C-Scorpionate Complexes of Fe(O3SCF3)2.

The complex [Fe(HL*)2](OTf)2, 1, where HL* = bis(3,5-dimethylpyrazol-1-yl)(3-1H-pyrazole)methane, was prepared in order to compare its magnetic properties with those of the analogous parent complex, [Fe(HL)2](OTf)2, that lacks methyl groups on pyrazolyl rings and that undergoes spin crossover (SCO) from the low spin (LS) to the high spin (HS) form above room temperature. It was anticipated that this new semibulky derivative should favor the HS state and undergo SCO at a lower temperature range. During this study, six crystalline forms of 1 were prepared by controlling the crystallization conditions. Thus, when reagents are combined in CH3CN, an equilibrium mixture of cis and trans isomers is established that favors the latter below 311 K. The trans isomer can be isolated exclusively as a mixture of solvates, LS trans-1·2CH3CN and HS trans-1·4CH3CN, by cooling CH3CN solutions to -20 °C with the former being favored at high concentrations and short crystallization times. Subsequently, vapor diffusion of Et2O into CH3CN solutions of pure trans-1·2CH3CN gives solvate-free HS trans-1. Subjecting trans-1·2CH3CN to vacuum at room temperature gives microcrystalline trans-1·CH3CN, identified by elemental analysis and its distinct powder X-ray diffraction pattern. If an isomeric mixture of 1 is subject to room-temperature vapor diffusion, then a crystalline mixture of HS isomers cis-1 and trans-1 is obtained. Finally, slowly cooling hot acetonitrile solutions of isomeric mixtures of 1 to room temperature gives large prisms of HS co-1, a species with both cis and trans isomers in the unit cell. The complexes trans-1, trans-1·CH3CN, cis-1, and co-1 undergo SCO below 250 K while trans-1·xCH3CN (x = 2, 4) solvates do not undergo SCO before desolvation.

4-(Benzofuran-2-yl)-2-[3-(4-chlorophenyl)-5-(4-fluorophenyl)-4,5-dihydro-1H-pyrazol-1-yl]thiazole

The molecule of the title compound, C26H17ClFN3OS, comprises benzofuranyl (A), thiazolyl (B), pyrazolyl (C), chlorophenyl (D) and fluorophenyl (E) ring systems. Rings A–D are almost coplanar, as indicated by the twist angles between the ring pairs A/B, B/C and C/D of 7.6 (1), 4.7 (1) and 6.9 (2)°, respectively. Ring E is twisted by 73.2 (1)° from the plane through ring C. In the crystal, pairwise C—H...F interactions link the molecules into inversion dimers. Aromatic π–π interactions are also observed between rings A and E and between rings B and C for neighbouring pairs of molecules related by inversion symmetry. Taken together, the weak interactions generate [010] chains.

Electronic and Photophysical Properties of ReI(CO)3Br Complexes Modulated by Pyrazolyl–Pyridazine Ligands

The direct reaction of a series of substituted (1H-pyrazol-1-yl)pyridazine (LI: 6-(1H-pyrazolyl)pyridazine; LII: 3-chloro-6-(1H-pyrazole-1-yl)-pyridazine; LIII: 6-(1H-3,5-dimethylpyrazolyl)pyridazine-3-carboxylic acid; LIV: 3,6-bis-N-pyrazolyl-pyridazine; and LV: 3,6-bis-N-3-methylpyrazolyl-pyridazine) with the bromotricarbonyl(tetrahydrofuran)-rhenium(I) dimer leads to the monometallic complexes [(LX)Re(CO)3Br] (I–V), which displays a nonregular octahedral geometry around the ReI center and a fac-isomerism for the carbonyl groups, whereas pyridazine and pyrazolyl rings remain highly coplanar after coordination to rhenium. Cyclic voltammetry shows one irreversible oxidation and one irreversible reduction for each compound as measured in N,N-dimethylformamide. Oxidation ranges from 0.94 V for III to 1.04 V for I and have been attributed to the ReI/ReII couple. In contrast, the reductions are ligand centered, ranging from −1.64 V for II to −1.90 V for III and V. Density functional theory calculations on the...

N′-[5-Acetyl-3-(4-bromophenyl)-2,3-dihydro-1,3,4-thiadiazol-2-ylidene]-5-(1H-indol-3-yl)-1-phenyl-1H-pyrazole-3-carbohydrazide dimethylformamide monosolvate

The main molecule of the title dimethylformamide monosolvate, C28H20BrN7O2S·C3H7NO, comprises bromophenyl (A), thiadiazolyl (B), pyrazolyl (C), phenyl (D) and indolyl (E) ring systems with twist angles between the planes through neigbouring rings A/B, B/C, C/D and C/E of 33.7 (1), 14.8 (1), 60.7 (2) and 20.9 (1)°, respectively. In the crystal, the molecules are related by c-glide symmetry to form columns parallel to [001] which are linked by intermolecular N—H...O, C—H...O and C—H...Br contacts.

3-{2-[3-(4-Chlorophenyl)-5-(4-fluorophenyl)-4,5-dihydro-1H-pyrazol-1-yl]thiazol-4-yl}-3,8a-dihydro-2H-chromen-2-one

The title compound, C27H17ClFN3O2S, comprises chromonyl (A), thiazolyl (B), pyrazolyl (C), chlorophenyl (D) and fluorophenyl (E) rings with twist angles between the planes of adjacent rings pairs A/B, B/C, C/D and C/E of 14.1 (1), 18.2 (2), 1.3 (1) and 4.9 (1)°, respectively. The crystal structure is characterized by a range of intermolecular interactions including C—H...F, C—H...Cl and C—H...O contacts. Aromatic π–π stacking between chromonyl groups and chlorophenyl groups [centroid–centroid separations = 3.7170 (16) and 4.017 (2) Å, respectively] lead to columns of molecules propagating parallel to the [100] direction.

5-[(4-Chlorophenyl)diazenyl]-2-[5-(4-fluorophenyl)-3-(furan-2-yl)-4,5-dihydro-1H-pyrazol-1-yl]-4-methylthiazole

The title compound, C23H17ClFN5OS, comprises fluorophenyl (A), furanyl (B), pyrazolyl (C), methylthiazoyl (D) and chlorophenyl (E) rings. The B–C–D–E linked ring system is close to planar with the dihedral angles B/C, C/D and D/E being 7.6 (1), 3.4 (1) and 8.4 (1)°, respectively. The fluorophenyl group is almost perpendicular to the pyrazoyl ring, as indicated by an A/C twist angle of 79.4 (1)°. In the crystal, inversion dimers linked by pairs of C—H...S contacts are observed.