942060-04-0Relevant articles and documents
Bidentate NHC pyrozolate ligands in luminescent platinum(ii) complexes
Naziruddin, Abbas Raja,Galstyan, Anzhela,Iordache, Adriana,Daniliuc, Constantin G.,Strassert, Cristian A.,De Cola, Luisa
, p. 8467 - 8477 (2015)
A bidentate C^N donor set derived from an N-heterocyclic carbene (NHC) precursor linked to a trifluoromethyl (CF3) functionalized pyrazole ring is described for the first time. The ligands have been employed to prepare four new phosphorescent complexes by the coordination of platinum(ii) centres bearing cyclometalated phenyl-pyridine/triazole-pyridine chelates. The electronic and steric environments of these complexes were tuned through the incorporation of suitable substituents in the phenyl-pyridine/triazole-pyridine ligands, wherein the position of the phenyl-ring substituent (a CF3 group) also directs the selective adoption of either a trans or a cis configuration between the CNHC and the Cphenyl donor atoms. Molecular structures obtained by X-ray diffraction for three of the complexes confirm a distorted square-planar configuration around the platinum centre, and DFT calculations show that the substituents have a significant influence on the energies of the frontier orbitals. Moreover, a platinum(ii) complex featuring the new bidentate NHC^pyrazolate ligand and a bulky adamantyl functionalized pyridine-triazole luminophore was observed to be highly emissive and exhibiting a sky-blue luminescence (λEm = 470 nm) with photoluminescence quantum yields as high as 50% in doped PMMA matrices. A complete photophysical investigation of all of the complexes in solution as well as in the solid state is herein reported.
A modified and practical synthetic route to indazoles and pyrazoles using tungstate sulfuric acid
Rahmatzadeh, S. Setareh,Karami, Bahador,Khodabakhshi, Saeed
, p. 17 - 20 (2015/02/19)
Tungstate sulfuric acid-catalyzed Knorr reaction have been used as a simple, rapid, atom economic and green method for the synthesis of indazole and pyrazole derivatives based on the condensation of hydrazine derivatives and ss-dicarbonyl compounds under solvent-free conditions. It was found that the catalyst could be recovered and reused without significant loss of its activity. The use of this method provides a novel and improved modification of Knorr synthesis in terms of clean reaction profile, use of a safe catalyst and solvent-free conditions. A green method for the synthesis of indazole and pyrazole derivatives from the condensation of hydrazine derivatives with dicarbonyl compounds has been described. Tungstate sulfuric acid (TSA) catalyzed efficiently the reactions to give good yields.
The effect of pressurized carbon dioxide on the cyclocondensation reaction between 4-alkoxy-1,1,1-trifluoro-3-alken-2-ones and hydrazines
Rossatto, Marcelo,Casanova, Caroline,Lima, Ana P.,Emmerich, Daniel J.,Oliveira, Vladimir,Dallago, Rogerio M.,Frizzo, Clarissa P.,Moreira, Dayse N.,Buriol, Lilian,Brondani, Sergio,Zanatta, Nilo,Bonacorso, Helio G.,Martins, Marcos A. P.
, p. 224 - 232 (2014/03/21)
The synthesis of 1-unsubstituted and 1-phenyl-5-trifluoromethylpyrazoles from the reaction of 4- alkoxy-1,1,1-trifluoro-3-alken-2-ones [CF 3C(O)CH=C(R1)OR, where R = Me, Et and R1 = H, Me, Ph] with hydrazines [NH2NHR2, where R2 = H, Ph] in pressurized carbon dioxide is reported for the first time. Reaction conditions such as pressure, temperature and time were evaluated. The methodology developed herein was suitable to synthesize products in moderate to excellent yields (60 % - 96 %) and short reaction times (15 - 45 min).
