冰水-溶液-炸药中耦合氢键的受激协同弛豫

Cooperativity of the coupled hydrogen bond of water ice,aqueous solutions,and energetic explosives

与传统定义的氢键(X…H)相比,耦合氢键(X:H-Y)集成分子间的X:H非键和分子内的H-Y成键作用(X=N,O;Y=X,C;而且H也可以被电负性较低的金属如Cu取代).耦合氢键具有两个显著的特征:一是它的分段长度、能量、和振动频率的协同性,二是其分段德拜比热的差异,其关键在于它的两端负电载体间的排斥耦合和极化作用.耦合氢键分段的德拜比热对温度的积分对应它们各自的结合能而德拜温度对应于振动频率.因此,我们可以通过施加外场(温度,压强,配位,电场,等)调制耦合氢键的极化和协同弛豫以改变氢键网络结构和氢键体系的物理性能.但是,耦合氢键的协同弛豫只有在Y-X排斥足够强和H-Y电负性差足够大的条件下发生.耦合氢键的建立使我们不仅能够定量破解关于水的结构和冰水的诸多反常物性,而且加深了对酸碱盐和有机溶液的氢键网络和属性以及氮基炸药的结构稳定性和储能机理等的系统认知.氢键耦合振子对的极化和协同弛豫为分子电子学提供了一个新的自由度以完整表述分子、电子、键合在时、空、能量域的受激行为.所以,由单分子基元动力学向耦合氢键和电子弛豫动力学的思维拓展,无论是对原子分子电子学的基础研究还是对实际工程应用都具有深远的意义.

With respect to the traditional definition(X···H),the coupled hydrogen bond(X:H-Y or HB)integrates the intermolecular(X:H)nonbond and the intramolecular H-Y polar covalent bond through X-Y repulsion(with":"being electron lone pair;X=N,O and Y=C,N,O in the presently discussed situations).The coupled hydrogen bond has two basic characteristics.One is the cooperativity of its segmental length,energy,and vibration frequency,and the other its specific heat capacities.The polarization and repulsion between the negative charge carriers of X and Y form the key.What is more important is that the integral of the Debye specific heat of each segment and its Debye temperature are correlated to its binding energy and vibration frequency,respectively.An external perturbation modulates the structure and performance of the bonding network through hydrogen bond cooperative relaxation and polarization.However,weaker X-Y repulsion or smaller electronegativity difference between H and Y may limit the hydrogen bond cooperativity.The establishment of coupled hydrogen bonds,and the associated HSymbolkB@H anti-HB and X:?:Y super-HB,enables us not only to resolve multiple anomalies such as floating and lubrication of ice,but also to deepen the systematic understanding of the hydrogen bond networks and properties of acidic,basic,salt and organic solutions,as well as the structural stability and energy storage mechanism of nitrogen-based explosive molecular assemblies.As a new degree of freedom,the coupling of intermolecular and intramolecular interactions enriches the molecular and electronic dynamics of lone pair involved systems for comprehensive information of the performance of bonds,electrons,and molecules in energetic,spatial,and temporal domains.