Four new Pd(II) complexes containing sulfonate-functionalized N-heterocyclic carbene ligands have been synthesized. All new complexes are palladium bis-NHCs, in which the ligands adopt a monodentate, bis-chelating, and pincer coordination form, so that a good comparison between their catalytic activities can be performed. The complexes have been used in the Suzuki−Miyaura cross-coupling reaction between aryl halides and phenylboronic acid in water and in i PrOH/water. The bis-NHC-palladium complex 1, in which the two NHC ligands are in a relative cis configuration, affords the best catalytic outcomes, with high TON values of 105 for 4-bromoacetophenone and 3.7 × 104 for 4-chloroacetophenone.

The formation of oligomeric soluble aggregates is related to the toxicity of amyloid peptides and proteins. In this manuscript, we report the use of a ruthenium polypyridyl complex ([Ru(bpy) 2 (dpqp)] 2+ ) to track the formation of amyloid oligomers at different times using photoluminescence anisotropy. This technique is sensitive to the rotational correlation time of the molecule under study, which is consequently related to the size of the molecule.[Ru(bpy) 2 (dpqp)] 2+ presents anisotropy values of zero when free in solution (due to its rapid rotation and long lifetime) but larger values as the size and concentration of amyloid-β (Aβ) oligomers increase. Our assays show that Aβ forms oligomers immediately after the assay is started, reaching a steady state at ∼48 h. SDS−PAGE, DLS, and TEM were used to confirm and characterize the formation of oligomers. Our experiments show that the rate of formation for Aβ oligomers is temperature dependent, with faster rates as the temperature of the assay is increased. The probe was also effective in monitoring the formation of α-synuclein oligomers at different times.

The UV irradiation of [Re(η 5 -C 5 Me 5 )(CO) 3 ] in the presence of C 6 F 6 effected intermolecular C᎐F and intramolecular C-H activation generating [Re(η 6 -C 5 Me 4 CH 2 )(CO) 2 (C 6 F 5 )] 1a in two isomeric forms. In the major isomer the CH 2 group lies trans to the C 6 F 5 group both in solution and in the crystal. In the minor isomer the CH 2 lies cis to the C 6 F 5 group. A similar reaction with C 6 F 5 CF 3 generates [Re(η 6 -C 5 Me 4 CH 2 )(CO) 2 (C 6 F 4 CF 3 )] 1b in four isomeric forms. In the major form the CF 3 group is in the 4 position and the CH 2 group lies trans to the C 6 F 4 CF 3 group. The other three isomers are formed by rotation of the η 6 -C 5 Me 4 CH 2 ligand as above, by placing the CF 3 at the 3 position, and by a combination of the two. Complex 1a reacted with PMe 3 to form the zwitterionic complex [Re(η 5 -C 5 Me 4 CH 2 PMe 3 )(CO) 2 (C 6 F 5 )] and with MeO Ϫ to form the anion [Re(η 5 -C 5 Me 4 CH 2 OMe)(CO) 2 (C 6 F 5 )] Ϫ , isolable as the NEt 4 ϩ salt. The reaction of 1a with HX (X = Cl or Br) generated cis-[Re(η 5 -C 5 Me 5 )(CO) 2 (C 6 F 5 )X] initially. More prolonged reaction led to the trans isomers. On reaction with HI, only the trans isomer was formed. Reaction of 1a with HBF 4 in Et 2 O in the presence of MeCN led to formation of the salt [Re(ηThe halogens Cl 2 , Br 2 and I 2 reacted to form (halogenomethyl)tetramethylcyclopentadienyl complexes trans-[Re(η 5 -C 5 Me 4 CH 2 X)(CO) 2 (C 6 F 5 )X] (X = Cl, Br or I). The bromo complex has been characterized crystallographically.

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Substituted amino-piperazine derivatives were synthesized and used as precursors for the preparation of a series of new organometallic Re(i) imine complexes with the general formula [(η-CHCH[double bond, length as m-dash]N-(CH)-Pz-R)Re(CO)] (Pz-R: -alkyl or aryl piperazine). The piperazine-based ligands were designed to be potential inhibitors of GSK-3β kinase. All the ligands and complexes were fully characterized and evaluated against the HT-29 and PT-45 cancer cell lines, in which GSK-3β plays a crucial role. In this context, we carried out biological evaluation using the MTT colorimetric assay. In terms of structure activity relationship, our findings indicated improved biological activity when aromaticity increased in the organic ligands (3d). In addition, the presence of the rhenium fragment in the imines (5a-d) leads to better activity with IC values in the range of 25-100 μM. In addition, our experimental studies were complemented by computational studies, where the volume and electrostatic surface of the organic ligands and organometallic compounds as well as their binding to the kinase protein are calculated.

The fulvene complexes (η 6 -C 5 Me 4 CH 2 )Re(CO) 2 R (1, R ) C 6 F 5 ; 2, R ) I) react at the exocyclic methylene carbon with allylmagnesium chloride or 2-thienyllithium to yield the anionic species). Further reaction with CH 3 I at room temperature affords the methyl complexes (η 5 -C 5 Me 4 CH 2 L)Re(CO) 2 (R)(Me) (3, R ) C 6 F 5 ; 4, R ) I). Protonation of the anionic species with HCl at low temperature gives the hydride complexes trans-Thermolysis of hexane solutions of 6, under CO atmosphere, produces the tricarbonyl complexes (η 5 -C 5 Me 4 CH 2 L)Re(CO) 3 (7) in moderate yields; if the reaction is carried out in the presence of PMe 3 , the analogous dicarbonyl phosphine derivatives (η 5 -C 5 Me 4 CH 2 L)Re-(CO) 2 (PMe 3 ) (9) are obtained, but no coordination of the lateral functionality is observed. In clear contrast, thermolysis of hexane solutions of the pentafluorophenyl hydride complexes trans-(η 5 -C 5 Me 4 CH 2 L)Re(CO) 2 (C 6 F 5 )(H), even under CO atmosphere, yields the chelated complexes (η 5 :η) 1). However, prolonged thermal treatment of 8b under a CO atmosphere affords the corresponding tricarbonyl complex 7b. The molecular structures of 8a and 9b have been determined. Both molecules exhibit formal three-legged piano-stool structures, with three terminal ligands in 9b (two CO and one PMe 3 ), but in the case of 8a, in addition to the two CO's, the third position corresponds to the η 2 -coordination of the butenyl substituent of the η 5 -C 5 Me 4 ring. Attempts to displace the coordinated sidearm in complex 8a have been investigated, as well as the photochemical reactions of tricarbonyl complexes 7.

Organometallic chalcone complexes functionalized with a macrocyclic fragment [( 5 -C 5 H 4 C(O)CH=CH-4-benzo-15-crown-5)MLn] (ferrocenyl, cyrhetrenyl, and cymantrenyl) have been synthesized. The complexes are characterized by IR spectroscopy, 1 H and 13 C NMR spectroscopies, elemental analyses, and HR-MS. The stereochemistry for the chalcone compounds was determined using the 1 H and 13 C NMR spectroscopy data, which indicated that they are isolated as a single isomer (E). In addition, the syntheses of the chalcone-imine derivatives are described, and they adopt an anti-(E,E) conformation in solution, confirmed by the X-ray crystal structures in the solid state. The UV-Visible and electrochemical behavior of the organometallic complexes are reported. Keywords: Organometallic chalcone and imine complexes, crown ether, crystal structures. examples of their application as chemosensors. Delavaux-Nicot et al. have investigated a series of ferrocenyl chalcones, mono and 1,1'-disubstituted, functionalized with an amine moiety or an aza-macrocycle. 13 These metallo-ligands have shown selectivity toward Ca 2+ and Ba 2+ in acetonitrile. Another important class of functionalized rhenium(I) complexes with aza-crown ether pendants, synthetized by Yam et al., exhibit a high specificity towardPb(II). 14 Previously, our research group reported the synthesis of new cyrhetrenyl tricarbonyl complexes functionalized with 4'-benzo-crown or 2-methyl-crown ether fragments, bridged by an imine linker. The cyclic voltammograms showed positive anodic waves arising from the Re(II)/Re(I) redox process (I). It was concluded that the size of the crown ether did not change the anodic potential significantly. Nevertheless, the metal centered redox processes of complexes that possess a methylene moiety were shifted to positive potentials compared to a benzo group. 15 In this work, we report the synthesis, X-ray structures and electrochemical and spectroscopic behaviour of new ferrocenyl, cyrhetrenyl and cymantrenyl complexes functionalized with 4'-benzo-15-crown-5 fragment. In addition we have included the synthesis of related species with a chalcone-imine as linker.2. Results and discussion. Synthesis of the organometallic chalcones 2-3.The compounds were synthesized following a procedure similar to that described for ferrocenyl and cymantrenyl chalcone derivatives. 11,16 It is based on the Claisen-Schmidt reaction involving the condensation of the organometallic ketones 1a-c and the corresponding crown ether or organic aldehydes Id-e (Scheme 1). Derivatives 2a-c and 3awere obtained by reaction of the corresponding precursors in the presence of NaOH and were dissolved in water/ethanol mixed solvent for greater solubility of the components. A modification of the experimental procedure was used for the preparation of the cyrhetrenyl derivative 3b. The carbanion containing solution was added dropwise to an ethanolic solution of terephthalaldehyde (Ie) over a period of 2 h. in order to control the proportion of nucleophile generated. The genera...