Synthesis and properties of isomeric pyridyl-containing chitosan derivatives.
Here we report on the method of synthesis in gel of a new heterocyclic aminopolymer-N-2-(4-pyridyl)ethylchitosan (4-PEC) via direct addition of 4-vinylpyridine to chitosan that yields a derivative with the substitution degree (DS) up to 0.8. The comparison of reactivity, thermal, spectroscopic, and sorption properties of a new derivative and its isomer N-2-(2-pyridyl)ethylchitosan (2-PEC) is presented. 2-PEC has higher sorption capacity and forms more stable chelates with [PdCl4](2-) and [PtCl6](2-) ions than 4-PEC, but the latter shows higher selectivity to noble metals ions in the presence of Cl(-) ions. A gradual increase of the sorption capacities and the affinity coefficient for Cu(2+) and Ni(2+) in the row chitosan<4-PEC<2-PEC was related to the increase of electron donor nitrogen atoms content and chelating properties of 2-PEC. A nearly negligible increase of the 4-PEC sorption capacity for Ag(+), as compared to plain chitosan, was suggested to be dependent on the difference in complexation models for 2-PEC and 4-PEC derivatives. The density functional theory (DFT) calculations have shown that the "pendant" model of the complex with Ag(I) is energetically favorable only for 2-PEC derivative, while in cases of chitosan and 4-PEC only "bridge" complexes can be formed that results in lower sorption capacity.
Institute of Chemistry, Far East Branch of RAS, 159, Prosp. 100-letiya Vladivostoka, Vladivostok 690022, Russia.
S Yu
SY
Bratskaya
Yu A
YA
Azarova
A S
AS
Portnyagin
A V
AV
Mechaev
A V
AV
Voit
A V
AV
Pestov
D048271:Chitosan / Q000031:analogs & derivatives / Q000737:chemistry*; D006860:Hydrogen Bonding; D052578:Ionic Liquids; D007536:Isomerism; D015394:Molecular Structure; D013816:Thermodynamics
D052578:Ionic Liquids; D048271:Chitosan
Chitosan; Physical–chemical properties; Pyridyl derivative