Substituted Tris(2-pyridylmethyl)amine Ligands for Highly Active ATRP Catalysts

Abstract

General:Materials. All chemicals were purchased from commercial sources, e.g., Aldrich, TCI, and used as received if not stated otherwise. Tris(2-pyridylmethyl) amine (TPMA) was purchased from ATRP Solutions. Methyl acrylate (MA) and butyl acrylate (BA) were passed through a column filled with basic alumina to remove inhibitor prior to use. All manipulations for atom transfer radical polymerizations were performed with oxygen free solvents, degassed by at least three Freeze-Pump-Thaw cycles (FPT), using standard Schlenk techniques. Instrumentation.Gel permeation chromatography (GPC): GPC was used to determine number average molecular weight (M n ) and M w /M n values. The GPC was conducted with a Waters 515 HPLC Pump and Waters 2414 Refractive Index Detector using PSS columns (Styrogel 10 2 , 10 3 , 10 5 Å) in tetrahydrofuran (THF) as an eluent at a flow rate of 1 mL/min at 35 o C. The column system was calibrated with 12 linear polystyrene (PSt, M n = 376~2,570,000) and 12 linear poly(methyl methacrylate) (PMMA, M n = 800 ~ 2,570,000) standards. Conversion of monomer was determined by 1 H NMR spectroscopy or gravimetrically. Absolute values of PMA may be calculated utilizing universal calibration as reported in literature. [1] NMR: Monomer conversion was measured using 1 H NMR spectroscopy, using a Bruker Avance 300 MHz or 500 MHz spectrometer at room temperature. For ligand synthesis, NMR spectra were measured using spectrometers at 300 MHz ( 1 H) and 75 MHz ( 13 C). All spectra were recorded in CDCl 3 and chemical shifts (δ) are reported in ppm relative to tetramethylsilane referenced to the residual solvent peaks. [2] Spectra were measured at room temperature unless otherwise stated. MS:Mass spectra were recorded on a mass spectrometer with a Varian Saturn 2100T MS with 3900 GC using an EI source. In each case, characteristic fragments with their relative intensities in percentages are shown. Electrospray mass spectra were measured on a Thermo-Fisher LCQ ESI/APCI Ion Trap containing a quadrupole field ion trap mass spectrometer with electrospray ionization (ESI).CV: All cyclic voltammograms (CV) were measured at 25 o C with a PARC 263A potentiostat.Solutions of CuBr 2 /TPMA* and Cu(OTf) 2 /TPMA* (1.0/1.0 mM) were prepared in dry solvent containing 0.1 M NBu 4 PF 6 as the supporting electrolyte. Measurements were carried out under a N 2 atmosphere at a scanning rate () of 0.1 V s -1 , using a glassy carbon disk and platinum mesh

Tris(2-pyridylmethyl)amine Based Ligands in Copper Catalyzed Atom Transfer Radical Addition (ATRA) and Polymerization (ATRP)

“…The large difference in K ATRP values can be attributed mostly to an increase in the activation rate constant (k a , 8400 M -1 s -1 v.s. 3.8 M -1 s -1 ), indicating that Cu I (TPMA *3 )Br should be much more active in ATRP, as confirmed by recently published study (91). …”

“…This approach indeed seems to be justified, as demonstrated in a recent study which showed that EDGs in the para-substituted 2,2′-bipyridine ligands can significantly enhance catalytic activity in ATRP (88). In a related work, inspired by the synthetic modifications of TPMA ligand for copper catalyzed oxygen activation (89) and iron mimicking site for methane monooxygenase (90), even more active Cu II X 2 /TPMA *3 (X=Br or Cl, TPMA *3 = tris((4-methoxy-3,5-dimethylpyridin-2-yl)methyl)amine) in situ system was discovered containing a total of nine EDGs (91). This catalyst attained excellent polymerization results in photoATRP (92)(93)(94) of acrylates and emerged as one of the most active ATRP systems nowadays.…”

“…The motivation towards development of synthetic methodologies for modification was largely driven by research in the area of copper catalyzed oxygen activation (12, 18-21, 25, 97). Recently, copper complexes with TPMA based ligands containing 4-methoxy-3,5-dimethyl substituted pyridine arms (TPMA *1-*3 ) were also successfully utilized in ATRA and ATRP reactions (Scheme 4) (91,98).…”

“…The selection of appropriate ATRP conditions is reliant on various factors such as monomer, initiator, ligand, solvent, etc. (59,74) Large K ATRP values require ATRP methods with constant regeneration of Cu I complex due to early termination reactions that typical occur under normal ATRP conditions (91,107). Therefore, in the present study, activators regenerated by electron transfer (ARGET) ATRP (56) of n-butyl acrylate (nBA) was targeted utilizing low amounts of Sn(EH) 2 as the reducing agent and only 10 ppm of the copper complexes with TPMA, TPMA *1 , TPMA *2 and TPMA *3 ligands.…”

Computer‐Aided Optimization of Conditions for Fast and Controlled ICAR ATRP of n‐Butyl Acrylate

“…[56][57][58][62][63][64] Such information is crucial for a comparison of these techniques to evaluate their potential industrial application, since the ultimate goal of a CRP technique is to produce a wide range of average chain lengths at acceptable polymerization rates while preserving control over PDI and EGF. In this work, such detailed kinetic modeling study is presented for the bulk ICAR ATRP of nBuA using the commercially available N,N,N 0 ,N 00 ,N 00 -pentamethyldiethylenetriamine (PMDETA)…”