Bismesitoylphosphinic Acid (BAPO‐OH): A Ligand for Copper Complexes and Four‐Electron Photoreductant for the Preparation of Copper Nanomaterials

Abstract

Bismesitoylphosphinic acid, (HO)PO(COMes) (BAPO-OH), is an efficient photoinitiator for free-radical polymerizations of olefins in aqueous phase. Described here are the structures of various copper(II) and copper(I) complexes with BAPO-OH as the ligand. The complex Cu (BAPO-O) (H O) is photoactive, and under irradiation with UV light in aqueous phase, it serves as a source of metallic copper in high purity and yield (>80 %). Simultaneously, the radical polymerization of acrylates can be initiated and allows the preparation of nanoparticle/polymer nanocomposites in which the metallic Cu nanoparticles are protected against oxidation. The determination of the stoichiometry of the photoreductions suggests an almost quantitative conversion from Cu into Cu with half an equivalent of BAPO-OH, which serves as a four-electron photoreductant.

Bis(acyl)phosphine Oxides as Stoichiometric Photo‐Reductants for Copper Nanoparticle Synthesis: Efficiency and Kinetics

“…In our model, C ⋅ transfers one electron to Cu 2+ (or Cu 1+ ), yielding a mono(acyl)phosphine oxide M (Reactions (4) and (5)). Alternatively, the phosphanoyl radical can also lead to cation P + (Reaction (3)) [42,47] . Importantly, the agglomeration of Cu atoms forming the nanoparticles must be included here, because this process causes the emerging absorption bands (Reaction (6)).…”

“…Alternatively, the phosphanoyl radical can also lead to cation P + (Reaction (3)). [42,47] Importantly, the agglomeration of Cu atoms forming the nanoparticles must be included here, because this process causes the emerging absorption bands (Reaction (6)). An additional source of Cu 0 is the disproportionation of Cu 1 + (Reaction (7)).…”

“…Bis(acyl)phosphane oxides (BAPOs) are highly active photoinitiators for photo‐induced radical polymerizations and are widely applied in industrial coating processes [27–37] In addition, BAPOs have been reported as photo‐reductants for Au + , Ag + and Pd 2+ salts [38–41] and also for obtaining of Cu + compounds from Cu 2+[42] salts and this process can be applied in photochemically initiated azide‐alkyne cycloadditions [43–46] . Some of us reported that a P‐hydroxylated derivative of BAPO, namely (HO)PO(COMes) 2 (=BAPO‐OH) can photo‐reduce Cu 2+ salts to Cu nanoparticles [47] . This reaction requires water as solvent, a pH range between 1–7, and rather long irradiation times (>1 h) to give good yields.…”

“…[43][44][45][46] Some of us reported that a P-hydroxylated derivative of BAPO, namely (HO)PO(COMes) 2 (= BAPO-OH) can photo-reduce Cu 2 + salts to Cu nanoparticles. [47] This reaction requires water as solvent, a pH range between 1-7, and rather long irradiation times (> 1 h) to give good yields. Elemental analysis indicated that one BAPO-OH molecule possibly serves as four electron reductant surpassing the efficiency of aromatic ketones and α-hydroxyketones as photo-reducing agents.…”

Bismesitoylphosphinic Acid (BAPO‐OH): A Ligand for Copper Complexes and Four‐Electron Photoreductant for the Preparation of Copper Nanomaterials

“…(3), and [Cu I (BAPO-O)] n (4). [23] Dotted squares indicate the equatorial planes of the Jahn-Teller distorted coordination spheres around copper(II) centers. a) 2 (ellipsoids at 50 %, selected Ha toms, THF, and one equivalent of co-crystallized 1a re omitted for clarity).…”