In the specific context of condensed media, the significant and increasing recent interest in the α-cyanostilbene (CS) motif [ArCHC(CN)Ar] is relevant. These compounds have shown remarkable optical features in addition to interesting electrical properties, and hence they are recognized as very suitable and versatile options for the development of functional materials. This progress report is focused on current and future use of CS structures and molecular assemblies with the aim of exploring and developing for the next generations of functional materials. A critical selection of illustrative materials that contain the CS motif, including relevant subfamilies such as the dicyanodistyrylbenzene and 2,3,3-triphenylacrylonitrile shows how, driven by the self-assembly of CS blocks, a variety of properties, effects, and possibilities for practical applications can be offered to the scientific community, through different rational routes for the elaboration of advanced materials. A survey is provided on the research efforts directed toward promoting the self-assembly of the solid state (polycrystalline solids, thin films, and single crystals), liquid crystals, nanostructures, and gels with multistimuli responsiveness, and applications for sensors, organic light-emitting diodes, organic field effect transistors, organic lasers, solar cells, or bioimaging purposes.

The quality of crystalline two-dimensional polymers (2DPs) 1-6 is intimately related to the elusive polymerization and crystallization processes. Understanding the mechanism of such processes at the (sub)molecular level is crucial to improve predictive synthesis and to tailor material properties for applications in catalysis 7-10 , and (opto)electronics 11, 12 , among others [13][14][15][16][17][18] . We characterize a model boroxine 2D dynamic covalent polymer, by using in situ scanning tunneling microscopy, to unveil both qualitative and quantitative details in the nucleation-elongation processes in real time and under ambient conditions. Sequential data analysis allows for the observation of the amorphous-to-crystalline transition, the timedependent evolution of nuclei, the existence of "nonclassical" crystallization pathways and importantly, the experimental determination of essential crystallization parameters including critical nucleus size, nucleation rate and growth rate with excellent accuracy. The experimental data has been further rationalized by atomistic computer models that altogether provide a detailed picture of the dynamic on-surface polymerization process. Furthermore, we show how two-dimensional crystal growth can be affected by abnormal grain growth (AGG). This finding provides support for the use of AGG -a typical phenomenon in metallic and ceramic systems -to convert a polycrystalline structure into a single crystal in organic and 2D material systems. Two-dimensional polymers (2DPs) -covalently linked networks of monomers in orthogonal directions-can be found as individual monolayers, as part of few-layer stacks, or as part of multilayered crystals, the latter known as 2D covalent organic frameworks (2D COFs). Over the past decade, research has focused on exploring efficient and controlled synthetic strategies to produce highly crystalline 2DPs [19][20][21][22][23][24][25][26] . Yet little is known about the mechanistic and kinetic aspects of the dynamic processes involving bond formation/breakage, nucleation,

Two-dimensional (2D) covalent organic frameworks (COFs) are an emerging class of promising 2D materials with high crystallinity and tunable structures. However, the low electrical conductivity impedes their applications in electronics and optoelectronics. Integrating large π-conjugated building blocks into 2D lattices to enhance efficient π-stacking and chemical doping is an effective way to improve the conductivity of 2D COFs. Herein, two nonplanar 2D COFs with kagome (DHP-COF) and rhombus (c-HBC-COF) lattices have been designed and synthesized from distorted aromatics with different π-conjugated structures (flexible and rigid structure, respectively). DHP-COF shows a highly distorted 2D lattice that hampers stacking, consequently limiting its charge carrier transport properties. Conversely, c-HBC-COF, with distorted although concave–convex self-complementary nodes, shows a less distorted 2D lattice that does not interfere with interlayer π-stacking. Employing time- and frequency-resolved terahertz spectroscopy, we unveil a high charge-carrier mobility up to 44 cm2 V–1 s–1, among the highest reported for 2D COFs.