Visible light-induced radical polymerization of vinyl acetate mediated by organo-nickel N2O2 Schiff-base complexes

Photo‐induced organo‐manganese‐mediated radical polymerization of acrylates under LED irradiation

“…These complexes were prepared with some modifications to literature procedures. 23,37,38 A solution of the Schiff base ligand (1.0 mmol) in methanol (30 mL) containing NaOH (2 mmol) was added dropwise to a Schlenk containing manganese (II) chloride (1 mmol). After refluxing the solution overnight, it was filtered under an N 2 atmosphere.…”

“…Four Schiff bases, two symmetrically and two new nonsymmetrically substituted N 2 O 2 tetradentate, along with their corresponding manganese (II) complexes, were synthesized with modifications to previously detailed procedures in the literature. 23,31,32,37,38 In this study, the Schiff bases were prepared by the condensing respective aldehydes with 1,3-diaminopropane in methanol under reflux condition, while the corresponding Mn (II) complexes were synthesized by reacting a methanolic solution of the appropriate ligand with the manganese (II) chloride in the presence of NaOH (Scheme 1). The Schiff base ligands (BuSalpen, Bu 2 Salpen, EthoxySalpen, and Ethoxy 2 Salpen) were fully characterized by FTIR, UV-Vis, and NMR spectroscopic techniques.…”

“…The photopolymerizations were systematically assessed by varying the concentrations of both the monomer (MA) and photoinitiator (TPO) during exposure to LED light at wavelengths of 390 nm and a range of 400-800 nm using the complexes Mn-Bu, Mn-Bu 2 , Mn-ethoxy, and Mn-Ethoxy 2 at 25 C. The photopolymerizations were first attempted using [MA]/[Mn II ]/[TPO] molar ratios of 900/1/1 and 600/1/1, based on a previous study (entries 1-8, Table 1). 23,31,32 The final conversions were around 20-65% within 10 min, and the polymers had a high dispersity (Đ) of 2.0-2.8 (entries 1-8, Table 1). Under these conditions, the photopolymerizations showed a low degree of control using the four Mn (II) complexes, probably because of the high radical concentration.…”

“…Therefore, photo-OMRP has become a popular technique because excellent spatial and temporal quality can be easily achieved by using the most suitable light sources with different LEDs (e.g., at 365, 390, and 400-800 nm), providing a versatile method for polymer synthesis. 22,23 A wide variety of transition metals, including Ti, V, Cr, Fe, Ni, Mo, Os, and Co, have been utilized in OMRP. 22,[24][25][26][27][28][29] Among these, Co (II) has been extensively explored in photo-OMRP because of the relatively weak Co-C bond.…”

“…30 Our research group has also investigated Co (II) and Ni (II) complexes bearing symmetrical and nonsymmetrically substituted N 2 O 2 tetradentate Schiff base ligands in the photo-OMRP of acrylates and vinyl acetate under LED irradiation at 390 nm and in the range of 400-800 nm. 23,31,32 Koumura et al reported that a dinuclear manganese carbonyl complex [Mn 2 (CO) 10 ] exhibits high effectiveness in achieving rapid and controlled radical polymerization of vinyl acetate under visible light in the presence of an alkyl iodide initiator. 33 However, to the best of our knowledge, there are no reports on photo-OMRP mediated by manganese complexes.…”