The coordination behaviour of the title ligand, 5-methyl-3-formylpyrazole N(4)-benzyl-N(4)-methylthiosemicarbazone(HMPz4BM), is reported with solid state isolation of copper(II) complexes, [Cu(HMPz4BM)X2] (X = Cl, Br, NO3, ClO4 and BF4) which have been spectroscopically and structurally characterised Ir data for the free ligand and its Cu(II) complexes indicate that HMPz4BM exhibits a neutral NNS tridentate function via the pyrazolyl nitrogen(tertiary), azomethine nitrogen and thione sulphur Electronic spectral data are suggestive of a square pyramidal environment for the seemingly pentacoordinated Cu(II) species Esr parameters (RT and LNT) of the reported copper(II) complexes are indicative of a dxx2–y2 ground state for the reported species Cyclic voltammograms of Cu(II) complexes show a quasireversible CuII/CuIII couple and also an irreversible CuII/CuI couple X-ray crystallography of a representative species, [Cu(HMPz4BM)(NO3)2] (C2/c, monoclinic ), has unambiguously documented the conjectural findings from ir data that coordinating sites of the title ligand are pyrazolyl (tertiary)nitrogen, azomethine nitrogen and the thione sulphur (NNS); and the oxygen of one of the nitrate ions has occupied the basal plane; the fifth coordination position has been occupied by the oxygen of another nitrate ion in a square pyramidal geometry The antibacterial properties of the ligand and its copper(II) complexes studied on microorganism, Staphylococcus aureus have pointed out that most of the complexes have higher activities than that of the free ligand

Spectroscopic, structural and antibacterial properties of copper(II) complexes with bio-relevant 5-methyl-3-formylpyrazole N(4)-benzyl-N(4)-methylthiosemicarbazone.

Synthesis and structural characterization of copper(II) and vanadium(V) complexes of pyridyl/pyrimidyl–pyrazole derived Schiff base ligands – Metal specific adjustment of ligand binding mode

Synthesis and structural characterization of three hydrogen-bonding connected supramolecular complexes of nickel, zinc and copper with 1,3-diphenyl-4-(salicylidene hydrazide)-acetyl-pyrazolone-5 and 2,2′-bipyridine

Herein, a new probe, 5-methyl-1-pyridin-2-yl-1H-pyrazole-3-carboxylic acid (1-pyridin-2-yl-ethylidene)-hydrazide (Hmppc), bearing a pyridine–pyrazole moiety, was synthesized, which offered potential for chemical sensing of Al3+. Investigations of the fluorescence behaviour of Hmppc in DMSO/H2O (2 : 8, v/v) solution under biologically relevant conditions in HEPES buffer (pH = 7.4) displayed a dramatic switch-on response to Al3+ as a result of chelation-induced enhanced fluorescence (CHEF). Detailed experimental studies reveal that Hmppc can detect Al3+ in solution with high sensitivity and selectivity, having a detection limit of 1.2 nM. Furthermore, to demonstrate the analytical potential of Hmppc, we validated our sensing system as a naked eye detector for Al3+. Interestingly, bioimaging studies on HepG2 cells demonstrated that Hmppc responded selectively towards Al3+, allowing real time detection of Al3+ in living cells.

A new fluorescence turn-on chemosensor for nanomolar detection of Al3+ constructed from a pyridine–pyrazole system

Tris(2-pyridylemthyl)amine (TPA) derivatives having two amide moieties at the 6-positions of the two pyridine rings of TPA and their Ru(II) complexes were synthesized and characterized by spectroscopic methods, X-ray crystallography, and electrochemical measurements. The complexes prepared were [RuCl(L)]PF(6) (L = N,N-bis(6-(1-naphthoylamide)-2-pyridylmethyl)-N-(2-pyridylmethyl)amine (1), N,N-bis(6-(2-naphthoylamide)-2-pyridylmethyl)-N-(2-pyridylmethyl)amine (2), N,N-bis(6-(isobutyrylamide)-2-pyridylmethyl)-N-(2-pyridylmethyl)amine (3)); the crystal structures of the three compounds were established by X-ray crystallography. In variable-temperature (1)H NMR spectra of 1 and 2 in CD(3)CN solutions, the pi-pi stacking in 1 was too rigid to exhibit any fluxional motions in NMR measurements; however, the pi-pi stacking of 2 was weaker and showed fluxional behavior in nearly T-shaped pi-pi interaction for the 2-naphthly groups (DeltaH degrees = -2.3 kJ mol(-1); DeltaG degrees = -0.9 kJ mol(-1) and DeltaS degrees = -7.7 J mol(-1) K(-1) at 233 K in CD(3)CN). For each of these three complexes, one of the amide moieties coordinated to the Ru(II) center through an amide oxygen. The other uncoordinated amide N-H formed intramolecular hydrogen bonding which remained intact even in aqueous media, indicating the intramolecular hydrogen bonding was geometrically compelled to form. The amide coordination is also stabilized and strengthened by the hydrogen bonding, so that the structure of each compound is maintained in solution. It is suggested that this hydrogen bonding lowers the redox potentials of the Ru(II) centers due to polarization of the coordinated amide C=O bond, in which the oxygen atom becomes more electrostatically negative and its electron-donating ability is strengthened. The N-H protons in the coordinated amide moieties were found to undergo a reversible deprotonation-protonation process, and the redox potentials of the Ru(II) centers could be regulated in the range of 500 mV in CH(3)CN solutions. The Pourbaix diagram for 1 clearly showed that this proton-coupled redox behavior is a one-electron/one-proton process, and the pK(a) value was estimated to be approximately 6.

Structures and Properties of Ruthenium(II) Complexes of Pyridylamine Ligands with Oxygen-Bound Amide Moieties: Regulation of Structures and Proton-Coupled Electron Transfer

Synthesis and spectroscopic characterisation of copper(II) complexes with 5-methyl-1-(2′-pyridyl) pyrazole-3-carboxamide (MPyPzCA): X-ray crystal structure of [Cu(MPyPzCA)2(H2O)](ClO4)2

Synthesis and spectroscopic characterization of cobalt(II), nickel(II) and copper(II) complexes with 5-methyl-1-(2'-pyridyl)pyrazole-3-carboxylic acid and 5-methyl-1-(4',6'-dimethyl-2'-pyrimidyl)pyrazole-3-carboxylic acid

The coordination mode of the title ligand, 1 ( synthesised for the first time and abbreviated as EMPyPzC and characterised by elemental analyses, mass, IR and 1 H-NMR spectral parameters), is investigated by way of isolation of its solid complexes of CoII, NiII and CuII with various counter ions, X (X = Cl, Br, NO3, SCN, BF4, ClO4, ½SO4) and their physicochemical identification. Magnetic and electronic spectral studies classify the reported bis-chelates as six coordinated distorted octahedral ones. A comparative study of IR spectra between the ligand and of its complexes indicate neutral bidentate (NN) behaviour of the ligand in all the species through pyrazolyl 2N and pyridyl 1¢N respectively and hence in all the cases the chromophore is MN 4 X 2 (M = CoII/ NiII/CuII) .The RT e.s.r. spectra of some of the Cu II complexes indicate dx 2 -y 2 as ground state rather than dz 2. Electrochemical studies of some of the CuII species demonstrate easy oxidative nature of CuII .

https://journals.sagepub.com/doi/pdf/10.3184/030823406779173613

Nimairatan Adhikari

Papers

Synthesis and spectroscopic characterisation of copper(II) complexes with 5-methyl-1-(2′-pyridyl) pyrazole-3-carboxamide (MPyPzCA): X-ray crystal structure of [Cu(MPyPzCA)2(H2O)](ClO4)2

Synthesis and spectroscopic characterization of cobalt(II), nickel(II) and copper(II) complexes with 5-methyl-1-(2'-pyridyl)pyrazole-3-carboxylic acid and 5-methyl-1-(4',6'-dimethyl-2'-pyrimidyl)pyrazole-3-carboxylic acid

Synthesis and spectroscopic characterisation of cobalt(II), nickel(II) and copper(II) complexes with 5-methyl-1-(2'-pyridyl)pyrazole-3-carbohydrazide