Département de chimie moléculaire

The search for copper catalysts able to perform effectively click reactions in water in the absence of sodium ascorbate is an active area of current research with strong potential for applications in bioconjugation. The water-sol. and photoreducible copper(II)-EDA (EDA = ethylenediamine) complex 1, which has two 4-benzoylbenzoates acting as both counterion and photosensitizer, has been synthesized and characterized by different techniques including single crystal X-ray diffraction. Highly efficient photoredn. was demonstrated when solns. of 1 in hydrogen atom donating solvents, such as THF or MeOH, were exposed to UVA radiation (350-400 nm) provided by a low pressure mercury lamp (type TLC = thin-layer chromatog., 365 nm), or by a 23 W fluorescent bulb, or by ambient/sunlight. In water, a much poorer hydrogen atom donating solvent, the photoredn. of 1 proved inefficient. Interestingly, EPR studies revealed that complex 1 could nonetheless be effectively photoreduced in water when alkynes were present in soln. The catalytic activity of 1 for click reactions involving a range of water-sol. alkynes and azides, in particular saccharides, was tested under various illumination conditions. Complex 1 was found to exhibit a photolatent character, the photogenerated copper(I) being very reactive. On irradiating aq. reaction mixts. contg. 1 mol {%} of 1 at 365 nm (TLC lamp) for 1 h, click reactions were shown to proceed to full conversion. [on SciFinder(R)]