Synthesis, characterization, reactivity and computational studies of new rhenium(I) complexes with thiosemicarbazone ligands derived from 4-(methylthio)benzaldehyde

Coordination Chemistry of Potentially S,N,Npy-Tridentate Thiosemicarbazones with the {Re(CO)3}+ Fragment and Formation of Hemiaminal Derivatives

“…In the present case, the intramolecular H-bond N2–H···N4 probably plays a stabilizing role in the structure by blocking the coordinative capacity of the pyridine fragment and maintaining the planarity of the TSC arm in the structure. The Re–S and Re–N bond distances are within the range observed previously for TSC complexes with rhenium­(I). ,,,− …”

“…The Re–S and Re–N bond distances are within the range observed previously for TSC complexes with rhenium(I). 5 , 9 , 19 , 21 − 25 …”

“…It is worth noting that the reaction involving the addition of base to chloroform led to the isolation of the tridentate thiosemicarbazonate complexes (vide supra). However, the formation of this type of dimer is not surprising, and the spontaneous formation of such species has been observed numerous times for TSCs, 8,19,24,25 either in the absence of the base or by forcing its formation by introducing NaOH into the medium. The tridentate capacity of the ligand is not an impediment to the formation of such dimers, as evidenced by TSCs derived from 4,6-diacetylresorcinol, 5 and their formation is probably favored by the low solubility of the dimers, which facilitates the separation of the complex from the reaction medium, in this case, MeOH.…”

Synthesis of Novel Dinuclear N-Substituted 4-(Dimethylamino)benzaldehyde Thiosemicarbazonates of Rhenium(I): Formation of Four- and/or Five-Membered Chelate Rings, Conformational Analysis, and Reactivity

“…Therefore, we reasoned that, to obtain the pure compounds, one should start from the previously isolated adducts [ReX­(HL)­(CO) 3 ] because analysis of the crystal structure of [ReBr­(κ 2 - S , N3 -HL B )­(CO) 3 ] (Chart ) confirmed the formation of this type of complex, in which only the conformation of the C1–N2 bond has been inverted. As observed previously, ,,, these types of structures (conformers) are far from unknown, at least in rhenium­(I) complexes. Although the production methods for these types of compounds involve relatively long reaction times at room or moderate temperatures (for instance, CHCl 3 under reflux), we observed that adduct formation with the ligands HL A/B is practically complete in 1 h in low-polarity solvents (acetone or chloroform).…”

“…The peculiarities of obtaining the majority of radiopharmaceuticals based on metal radioisotopes (i.e., as rapid a synthesis as possible in the radiotherapy unit, administration of the reaction mediumphysiological serumto the patient with hardly any purification, and avoiding the presence of byproducts that may lead to uncertainty in the diagnostic test) are fundamental factors in the choice of the appropriate system. , In the course of our investigations into the design of molecules for radioimaging diagnosis using 99m Tc, we used different types of thiosemicarbazones to endow the final molecule with an affinity for biomolecules related to different pathologies. , The choice of this type of ligand was based on the hypothesis of the guaranteed formation of five-membered chelate rings (κ 2 -S,N3), with the thiosemicarbazone chain supplemented by the presence of substituents at C2 that provide additional donor groups. , However, in the course of our investigation, we observed the presence of thiosemicarbazone ligands with κ 2 -S,N2 coordination in mononuclear and polynuclear complexes. More recently, we also observed the formation of both types of chelates in the reaction media to obtain complexes of {Re­(CO) 3 } + derivatives with 4-(dimethylamino)­benzaldehyde thiosemicarbazone (HL).…”