Cymantrene–Triazole “Click” Products: Structural Characterization and Electrochemical Properties

Abstract

ABSTRACT:We report the first known examples of triazolederivatised cymantrene complexes (η 5 -[4-substituted-triazol-1-yl]cyclopentadienyl tricarbonyl manganese(I), obtained via a "click" chemical synthesis, bearing either a phenyl, 3-aminophenyl or 4-aminophenyl moiety at the 4-position of the triazole ring. Structural characterization data using multinuclear NMR, UV-vis, ATR-IR and mass spectrometric methods are provided as well as crystallographic data for (η 5 -[4-phenyltriazol-1-yl]cyclopentadienyl tricarbonyl manganese(I) and (η 5 -[4-(3-aminophenyl)triazol-1-yl]cyclopentadienyl tricarbonyl manganese(I). Cyclic voltammetric characterization of the redox behaviour of each of the three cymantrene-triazole complexes is presented together with digital simulations, in situ infra-red spectroelectrochemistry and DFT calculations to extract the associated kinetic and thermodynamic parameters. The trypanocidal activity of each cymantrene-triazole complex is also examined and found to be more active than cymantrene alone.

Synthesis and characterization of redox active cyrhetrene–triazole click products

“…16 Molina has reported click reactions applied to organometallic sandwich complexes such as ferrocene, 17 whilst the work conducted by Astruc has shown dendrimers can be modified with metallocenes and organometallics via a click chemistry reaction. 18 In contrast to the behaviour of 1, and the manganese(I) cymantrene-triazole derivatives reported previously by our group, 19 the two new cyrhetrene-triazole complexes reported herein are found to exhibit redox active behaviour of the triazole ligand moiety that prevents them acting as metal-based electron-transfer mediators.…”

“…Single crystals of 3 were grown by diffusion of petroleum ether into a saturated CH 2 Cl 2 solution of the compound at room temperature; an appropriate crystal was selected and data collected by the EPSRC National Crystallographic Service at the University of Southampton, where the data was reduced and an absorption correction performed Using Olex2, 25 the structure was solved and space group assigned with SuperFlip/EDMA 26 using charge flipping, and then refined with the ShelXL (version 2014/3) 27 refinement program using least squares minimisation. Two unassigned electron density peaks (5.8, 4.7 e.A -3 ) were observed in the asymmetric unit approximately 2.5 Å from each rhenium centre; such peaks were previously observed for the isostructural manganese analogue 19 in which case they were modelled as low occupancy (3%) manganese atoms, however in this case it was decided to leave them unassigned since doing so does not adversely affect the molecular structure of the species of interest. …”

“…3 Our first attempt at the copper-catalysed azide/alkyne cycloaddition of 3 was achieved using the conditions we have previously reported for the manganese variant of cyrhetrene {Scheme 1, (iii)}. 3,19,20 Reassuringly, the transformation of 2 into 3 was complete in 8 hours under these mild conditions; purification of 3 via silica gel flash column chromatography afforded 3 as a white crystalline solid in good yield and high purity (Scheme 1). [a] An extra band is observed in the asymmetric region for samples run in the solid state as a result of hindered rotation about the Re-Cp centroid and a subsequent descent in symmetry.…”

“…19,23 Single crystals of 3 were grown by diffusion of petroleum ether into a saturated CH 2 Cl 2 solution of the compound at room temperature and a X-ray crystal structure obtained ( Figure 1, bond lengths and angles detailed in tables S1 and S2). The structure is comparable to our previously reported manganese analogue 19 …”

“…19 The voltammetric behaviour of 4 recorded under identical conditions as described above is shown in Figure 3 and Figure S7. Single crystals of 3 were grown by diffusion of petroleum ether into a saturated CH 2 Cl 2 solution of the compound at room temperature; an appropriate crystal was selected and data collected by the EPSRC National Crystallographic Service at the University of Southampton, where the data was reduced and an absorption correction performed Using Olex2, 25 the structure was solved and space group assigned with SuperFlip/EDMA 26 using charge flipping, and then refined with the ShelXL (version 2014/3) 27 refinement program using least squares minimisation.…”