Poly(2‐methyl‐2‐oxazoline)‐polyethylenimine (PMeOx‐co‐PEI) copolymers differing by degree of polymerization (DP = 50 and 200) and PEI content (from 37 to 99 mol%) were synthesized by living cationic ring‐opening polymerization of 2‐methyl‐2‐oxazoline, followed by partial hydrolysis. Upon mixing with DNA in a wide range of N/P ratios, they formed well‐defined polyplex particles of small size (typically below 100 nm) and narrow size distribution. The polyplexes demonstrated good colloidal stability and very low in vitro cytotoxicity. The copolymers exhibited buffering capacity of over 50% relative to that of the reference PEI implying effective endo‐lysosomal escape of the polyplexes. Increased cellular internalization of both PCR fragments and plasmid DNA, attributable to the strongly positive ζ potential and small size of the polyplexes, was observed. In spite of these favorable prerequisites, the transfection efficiency was low (below 20% relative to the control PEI) and was attributed to retarded swelling of the polyplex particles, endo‐lysosomal rupture, and DNA release.
Copper(II)-catalyzed C-H/C-H coupling of dipolar 2-H-benzothiazoles end-capped with triphenylamine moieties affords highly fluorescent 2,2'-bibenzothiazoles with D-π-A-π-D architecture displaying large two-photon absorption (TPA) crosssections (5431252 GM) in the near-infrared region. The notably higher TPA performance as compared to quadrupolar π-systems with a widely-used 2,2'-bipyridine core, along with the ease of the synthesis and chelating N^N ability makes the title biheteroaryl platform an attractive building block for a large scope of functional dyes exploiting nonlinear optical phenomena.
One-pot reductive N,N-dimethylation
of suitable nitro- and amino-substituted (hetero)arenes can be achieved
using a DMSO/HCOOH/Et3N system acting as a low-cost but
efficient reducing and methylating agent. The transformation of heteroaryl-amines
can be accelerated by using dimethyl sulfoxide/oxalyl chloride or
chloromethyl methyl sulfide as the source of active CH3SCH2
+ species, while the exclusion of HCOOH
in the initial stage of the reaction allows avoiding N-formamides as resting intermediates. The developed procedures are
applicable in multigram-scale synthesis, and because of the lower
electrophilicity of CH3SCH2
+, they
also work in pathological cases, where common methylating agents provide N,N-dimethylated products in no yield or
inferior yields due to concomitant side reactions. The method is particularly
useful in one-pot reductive transformation of 2-H-nitrobenzazoles to corresponding N,N-dimethylamino-substituted heteroarenes. These, upon Cu(II)-catalyzed
oxidative homocoupling, afford 2,2′-bibenzazoles substituted
with dimethylamino groups as charge-transfer N^N ligands with intensive
absorption/emission in the visible region. The fluorescence of NMe2-functionalized bibenzothiazoles remains intensive even upon
complexation with ZnCl2, while emission maxima are bathochromically
shifted from the green/yellow to orange/red spectral region, making
these small-molecule fluorophores, exhibiting large emission quantum
yields and Stokes shifts, an attractive platform for the construction
of various functional dyes and light-harvesting materials with tunable
emission color upon complexation.
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