In order to explore the essence of the hydration process of chitin or chitosan in the presence of cation, the cooperativity effects between the H-bonding and Na⁺···molecule interactions in the 1,4-dimethoxy-d-glucosamine (DMGA) complexes with H₂O and Na⁺ were investigated at the B3LYP/6-311++G(d,p), M06-2X/6-311++G(2df,2p), and ωB97X-D/6-311++G(2df,2p) levels. The result shows that the complexes in which Na⁺ or H₂O is bonded simultaneously to the –NH and –OH groups connected to the C3 atom of DMGA are the most stable. The cooperativity and anti-cooperativity effects occur in DMGA···H₂O···DMGA and DMGA···Na⁺···H₂O, while only the cooperativities are confirmed in DMGA···Na⁺···DMGA. The cooperativity occurs in the DMGA···Na⁺···H₂O complexes without the hydration, while the anti-cooperativity occurs in those with the hydration. Furthermore, the cooperativity and anti-cooperativity in DMGA···Na⁺···H₂O are far stronger than those in DMGA···Na⁺···DMGA or DMGA···H₂O···DMGA. Therefore, a deduction is given that the cooperativity and anti-cooperativity effects play an important role in the hydration of chitin or chitosan in the presence of Na⁺. When only Na⁺ is linked with –OH and –NH groups of chitosan or chitin, due to the cooperativity effect, the hydration does not occur. When both Na⁺ and H₂O are linked with –OH and –NH groups, the anti-cooperativities are dominant in controlling of the aggregation process of Na⁺, H₂O, chitosan, and chitin, leading to the possible hydration. Atoms in molecules (AIM) analysis confirms the cooperativity and anti-cooperativity effects.

Graphical abstract

中文翻译：

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1,4-二甲氧基-D-葡萄糖胺络合物与Na +和H2O协同作用的理论研究。

为了探索在阳离子存在壳多糖或脱乙酰壳多糖的水合过程的本质，该氢键和Na之间的协同效应⁺ ...在1,4-二甲氧基-分子相互作用d -葡糖胺（DMGA）在B3LYP / 6-311 ++ G（d，p），M06-2X / 6-311 ++ G（2df，2p）和ωB97X-D/ 6-311处研究了具有H ₂ O和Na ^+的配合物++ G（2df，2p）级。结果表明，其中Na ⁺或H ₂ O同时与连接至DMGA的C3原子的-NH和-OH基团键合的配合物最稳定。DMGA···H ₂ O···DMGA和DMGA···Na ⁺ ···H ₂产生协同作用和反协同作用O，而在DMGA···Na ⁺ ···DMGA中仅确认了协同作用。没有水合的DMGA···Na ⁺ ···H ₂ O络合物中发生协同作用，而发生水合的化合物出现抗协同作用。此外，DMGA··Na ⁺ ·· H ₂ O中的协同性和反协同性比DMGA··Na ⁺ ··DMGA或DMGA··H ₂ O··DMGA中的强。因此，可以推断出在Na ⁺存在下，协同作用和反协同作用在甲壳质或壳聚糖的水合中起重要作用。当只有Na ⁺由于壳聚糖或几丁质的–OH和–NH基团具有协同作用，因此不会发生水合作用。当Na ⁺和H ₂ O都与–OH和–NH基团连接时，抗合作性在控制Na ⁺，H ₂ O，壳聚糖和几丁质的聚集过程中占主导地位，从而导致可能的水合。分子中的原子（AIM）分析证实了协同作用和反协同作用。

图形概要