This review is aimed at providing an in-depth understanding of the potential of post-synthetic strategies for the modification of covalent organic frameworks.

Matrix effects on the optimized geometries and the electronic properties of acid−base complexes XHB, with HX = HF, HCl, HBr, HCN and B = NH3, have been modeled using ab initio methods (6-31G** and 6-311++G** basis sets) in two different ways. Model A corresponds to the Onsager SCRF model, and model B corresponds to a homogeneous electric field F = 2qe 0/r e 2 = 2.88 × 105 q V/cm of varying strength generated by two distant charges +qe 0 and −qe 0 of opposite sign placed at distances of r e = 100 Å. In both models, the minima and reaction coordinate of proton transfer has been calculated. As the electric interactions are increased, both models predict an increase of the dipole moments associated with a proton shift from X to B, i.e., a conversion of the molecular to the zwitterionic complexes. Both models predicts double minima for some electric fields; in model B electric fields are found where the neutral complex is not stable, evolving to the ion pair complex. These fields can be used to characterize the acidity of the donor toward the base without the necessity of assuming a proton-transfer equilibrium. In both models a similar field-induced correlation between the two hydrogen bond distances r 1 ≡ X···H and r 2 ≡ H···B is observed for all configurations. This correlation indicates in the molecular complexes a hydrogen bond compression when the proton is shifted toward the base and in the zwitterionic complexes a widening. The minimum of the X···B distance r 1 + r 2 occurs when the proton-transfer coordinate r 1 − r 2 = r 01 − r 02, where r 01 and r 02 represent the distances X···H and H···B+ in the free donors.

Dipyrazino[2,3-f:2′,3′-h]quinoxaline also known as 1,4,5,8,9,12-hexaazatriphenylene (HAT) is an electron deficient, rigid, planar, aromatic discotic system with an excellent π–π stacking ability. Because it is one of the smallest two-dimensional N-containing polyheterocyclic aromatic systems, it has been used as the basic scaffold for larger 2D N-substituted polyheterocyclic aromatics. Furthermore, it is the building block of choice in a plethora of molecular, macromolecular and supramolecular systems for a variety of applications. This review is aimed to critically review the research performed during the almost three decades of research based on HAT from the synthetic, theoretical and application points of view. The design principles and synthetic strategies towards HAT derivatives will be established and their use in n-type semiconductors, sensors, nonlinear optical chromophores, liquid crystals, microporous polymers for energy storage and nano and microstructures will reveal the relevance of HAT as a basic scaffold in the areas of organic materials and nanoscience.