School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore.
Nanoscale. 2010 Oct;2(10):1930-61. doi: 10.1039/c0nr00245c. Epub 2010 Sep 2.
Although they exist ubiquitously in human bodies and our surroundings, the impact of nonbonding lone electrons and lone electron pairs has long been underestimated. Recent progress demonstrates that: (i) in addition to the shorter and stronger bonds between under-coordinated atoms that initiate the size trends of the otherwise constant bulk properties when a substance turns into the nanoscale, the presence of lone electrons near to broken bonds generates fascinating phenomena that bulk materials do not demonstrate; (ii) the lone electron pairs and the lone pair-induced dipoles associated with C, N, O, and F tetrahedral coordination bonding form functional groups in biological, organic, and inorganic specimens. By taking examples of surface vacancy, atomic chain end and terrace edge states, catalytic enhancement, conducting-insulating transitions of metal clusters, defect magnetism, Coulomb repulsion at nanoscale contacts, Cu(3)C(2)H(2) and Cu(3)O(2) surface dipole formation, lone pair neutralized interface stress, etc, this article will focus on the development and applications of theory regarding the energetics and dynamics of nonbonding electrons, aiming to raise the awareness of their revolutionary impact to the society. Discussion will also extend to the prospective impacts of nonbonding electrons on mysteries such as catalytic enhancement and catalysts design, the density anomalies of ice and negative thermal expansion, high critical temperature superconductivity induced by B, C, N, O, and F, the molecular structures and functionalities of CF(4) in anti-coagulation of synthetic blood, NO signaling, and enzyme telomeres, etc. Meanwhile, an emphasis is placed on the necessity and effectiveness of understanding the properties of substances from the perspective of bond and nonbond formation, dissociation, relaxation and vibration, and the associated energetics and dynamics of charge repopulation, polarization, densification, and localization. Finding and grasping the factors controlling the nonbonding states and making them of use in functional materials design and identifying their limitations will form, in the near future, a subject area of "nonbonding electronics and energetics", which could be even more challenging, fascinating, promising, and rewarding than dealing with core or valence electrons alone.
尽管非键合孤电子和孤电子对在人体和周围环境中普遍存在，但它们的影响长期以来一直被低估。最近的研究进展表明：（i）除了在物质转变为纳米尺度时短而强的键合作用会引发原本常数的体相性质的尺寸趋势外，在断裂键的附近存在孤电子会产生块状材料所不具备的迷人现象；（ii）与 C、N、O 和 F 四面体配位键相关的孤电子对和孤电子对诱导的偶极子形成了生物、有机和无机标本中的功能基团。本文以表面空位、原子链端和台面边缘态、催化增强、金属团簇的导电-绝缘转变、缺陷磁性、纳米尺度接触处的库仑排斥、Cu(3)C(2)H(2)和 Cu(3)O(2)表面偶极子形成、孤对电子中和界面应力等为例，重点介绍非键合电子的能量学和动力学理论的发展和应用，旨在提高人们对其对社会产生的革命性影响的认识。讨论还将扩展到非键合电子对催化增强和催化剂设计、冰的密度异常和负热膨胀、B、C、N、O 和 F 诱导的高温超导、CF(4)在合成血液抗凝中的分子结构和功能、NO 信号和酶端粒等奥秘的潜在影响。同时，强调了从键和非键形成、解离、松弛和振动以及相关的电荷再分布、极化、致密化和局域化的能量学和动力学角度理解物质性质的必要性和有效性。寻找和把握控制非键合态的因素，并将其应用于功能材料设计中，同时识别其局限性，将在不久的将来形成一个“非键合电子学和能量学”的研究领域，其挑战性、趣味性、前景和回报可能比单独处理核心或价电子更为可观。
