Synthesis, characterization, crystal structures and computational studies on novel cyrhetrenyl hydrazones

Abstract

A b s t r a c t:The synthesis of novel cyrhetrenyl hydrazones of general formula [Re{(η 5 -C 5 H 4 )-C(R 1 )=NNHR 2 }(CO) 3 ] {with R 1 = H and R 2 = 4-NO 2 -C 6 H 4 (4a), C 6 H 5 (4b) or H (4c) or R 1 = Me and R 2 = 4-NO 2 -C 6 H 4 (5a), C 6 H 5 (5b) or H (5c)} is described. Compounds 4a-4c and 5a-5c were characterized by mass spectrometry and IR spectroscopy. 1 H and 13 C{ 1 H} NMR studies revealed that 4a-4c and 5a-5c adopt the anti-(E) configuration in solution. X-ray crystal structures of compounds 4a and 5c confirmed the trans-arrangement of the cyrhetrenyl "Re(η 5 -C 5 H 4 )(CO) 3 " and the -NHR 2 moieties and the existence of strong hydrogen bonds involving the -NH-unit. Molecular Orbital calculations at a DFT level have also been carried out in order to rationalize the influence of the nature of the substituent R 3 of [R 3 CH=NNH(4-NO 2 -C 6 H 4 )] (R 3 = ferrocenyl, (3a), cyrhetrenyl (4a) and phenyl (6a) on the electronic delocalization, the nucleophilicity of the imine carbon, the polarizability and hyperpolarizability of these compounds, and computational studies using time-dependent density functional (TD-DFT) calculations have also been carried out in order to assign the bands detected in their electronic spectra and to explain the effect produced by the solvent.

New sulfonamides containing organometallic-acylhydrazones: synthesis, characterisation and biological evaluation as inhibitors of human carbonic anhydrases

“…In fact, the downfield shift observed for the cyrhetrenyl ( 1a – c ) and cymantrenyl ( 2a – c ) derivatives (Δδ∼0.5) compared with ferrocenyl analogues ( 3a – c ) can be related to the electron-withdrawing properties of the (η 5 -C 5 H 4 )M(CO) 3 moieties 33 , 34 , which produce a deshielding of the NH resonance, thus suggesting that the nature of the organometallic framework modifies the degree of electronic delocalization on the –C(H)=N–NH– unit. We have found similar results for ferrocenyl and cyrhetrenyl hydrazones 19 , 35 and 1,3,4-thiadiazoles 36 . In the case of the acylhydrazones 1c , 2c and 3c , additional signals were observed at 6.44 ppm, 3.36 ppm and 2.80–2.42 ppm, respectively.…”

Bioorganometallic derivatives of 4-hydrazino-benzenesulphonamide as carbonic anhydrase inhibitors: synthesis, characterisation and biological evaluation

“…In addition, a signal due to the methyl protons of the -C(CH 3 )¼N-fragment was also observed at approximately d 2.1 for compounds 1b, 2b and 3b. These results are in agreement with the values reported for organic 39 and organometallic analogues 40,41 observed between 8.16 and 7.11 ppm were assigned to the hydrogen atoms of the C 6 H 4 ring. As per literature reports, the broad singlet observed at 6.90-6.28 ppm was assigned to the hydrogen nuclei of the SO 2 NH 2 group 42,43 .…”

ELECTROCHEMICAL, ESR, THEORETICAL STUDIES AND in vitro ANTI-T. cruzi ACTIVITY OF 2-ORGANOMETALLIC-5-NITRO-BENZIMIDAZOLES

“…This phenomenon may be correlated with the electron-withdrawing property of the cyrhetrenyl moiety present in Bzn-1, compared to the electron-donating effect of the ferrocenyl fragment present in the analogue Bzn-2. Similar conclusions were previously reported by our group for hydrazones [79] and sulfonamides series [80] containing these organometallic moieties. Due to Fukui function, which is an important reactivity indicator in the framework DFT theory [60], we analyzed the condensed Fukui functions for Bzn-1 and Bzn-2 to explore which atoms are potential reactive sites for electrophilic, nucleophilic or radical attacks, respectively.…”