Covalent bonding occurs when pairs of electrons are shared by atoms. Atoms will covalently bond with other atoms in order to gain more stability, which is gained by forming a full electron shell. By sharing their outer most (valence) electrons, atoms can
Pauling improved the Heitler–London picture of the chemical bond by giving even homoatomic bonds a certain ionic contribution, which gave rise to valence bond (VB) theory12. This mixing of ionic terms into the covalent wave function does not only lower the total energy—which is called resonan...
because of their tendency to pair all valence electrons through strong covalent bonds to prevent the formation of unpaired spin-polarized electrons. Therefore, it is very surprising and exciting to see the most recent experimental observation of ferromagnetism in a two-dimensional (2D)sp2carbon-conjuga...
nonclassical effects, such as polarization of the covalent O–H bonds and softening of the lattice, leading to changes in proton-hopping barriers. For example, earlier work found that, even in nonpolar compounds, external electric field lowers the formation energy of oxygen vacancies due to polariz...
between carbon atoms in CPs is not a single σ bond, as in flexible organic polymers, but the combination of σ and π bonding that originates from the delocalization of π electrons along the length of the polymer, which prevents the rotation of the chain along the chemical bonds. The...
Porous polymers are generally bonded by stable covalent bonds and can be divided into hypercrosslinked polymers (HCPs), polymers of intrinsic microporosity (PIMs), covalent organic frameworks (COFs), conjugated microporous polymers (CMPs), and coordination porous polymers (CPP). Conjugated microporous po...
The highly electronegative state of B could effectively improve the Ni oxidation state as this highly electronegative cation could draw more electron density away from the Ni atom, resulting in a less covalent bond between Ni and O atoms. The increased high valence state of Ni species would be ...
ROS formation initially occurs with the binding of NADPH to the dehydrogenase domain, and the electrons are transferred sequentially from the NADPH substrate to the FAD cofactor and then to the two heme groups in the transmembrane domain. On the other side of the membrane, the final electron ...
5. In these materials, the atoms are strongly bonded by covalent or ionic bonds along the intrachain direction but mediated by weak vdW forces along the interchain direction, which results in significantly anisotropic electronic, and structural properties. For example, K2Cr3As386, Cs2Cr3As387 and...
and near-infrared (NIR) aqueous-related afterglow has been observed through forming covalent bonds between CDs and colloidal silica or constructing special p–n junction in carbon-based structures, their afterglow lifetimes are all shorter than one second31,32. Such a short duration of afterglow ...