Authors: Xinmiao Xie | Ying Wei | Dongqing Lin | Chunxiao Zhong | Linghai Xie | Wei Huang
Source: Chinese Journal of Chemistry (article, 2019-11-07)
Field: Materials Science — Materials Chemistry

Nanogridarene: A Rising Nanomolecular Integration Platform of Organic Intelligence In the background of organic electronics, nanogridarenes with the criteria of well-defined edge and extendable vertexes were discovered toward chemical intellibots in 2014. Herein, Friedel-Crafts Gridization (FCG) as the molecular installing technology (MIT) will be highlighted to synthesize various monogrids, multigrids and polygrids that would be potential cornerstone of covalent window, molecular integration and circuit as well as organic robots. The partial scenario of the time on earth is that the last century is the information age from silicon to computer while the 21st century is the era of consciousness from carbon to intellibot (ibot). The initial action of the millennium will impact the history of future thousand years. Heeger et al. discovered the conductivity of organic polymers to remove the obstacle along the tube of ibot in 1976 and won a Nobel prize in chemistry in 2000. After the commercialization of large-area OLEDs, flexible electronics would further create the fourth clothes of the human being that energize IoT smart by means of the surface-equals-device (SED) engineering. More recently, an independent supercycle of matter from atom to artificial chemists becomes clear in consideration of many frontier areas, such as auto-chemistry, molecular machine, soft robots, memristor-based neurocomputing, artificial intelligence and brain-machine interface as well as 3D printing. However, the molecular “God particle” still misses that plays an irreplaceable role in gluing all the horizontal techniques into one entities if the centurial picture becomes the truth from organics to robots. The innovation of organic ibots would require activating all potential features in organics such as atomic precise and quantum mechanism, step-by-step hierarchy, diversity and wide-range state of matter for the handling of four-level intelligence.1 According to the trend of chemistry that is inorganics toward smaller but organics toward larger, a molecular integration approach to the multichannel of various electrons, photons, excitons, ions, mechanons and/or other functons, (a combination of the word function and the suffix –on) was proposed from π-active covalent gridization that can be tuned by e-donor-acceptor (DA), steric attractor- repulsor (AR) and multiscale nanoarchitecture (NA) design under the collection and accumulation philosophy. The unprecedented molecular ontology of organic nanogrids that can integrate all three designs of the DA, AR and NA at the molecular level was first designed with the Chinese symbol of 日shape in 2014.2 Five types of monogrids have been designed since then. They are ladder-type, angle-lost, windmill-type, diamond-type and Tic-tac-toe-type according to the basic extension direction of fluorene reactive site at the 2-position (Figure 1). Two difluorene and two carbazole can make a robust ladder-type gridarene (LG) that has four arms with two pair of parallel directions.3 If 3-position of carbazole directly links with fluorene at the 2-position, the angle-lost grid (ALG) was installed that is similar to the famous lithograph art of Drawing Hands by the Dutch artist M. C. Escher. As a result, Drawing Hands-type Grid (DHG) as ALG is a potential covalent multibond for the nanolinkage of nanoobjects. Fluorene combined with straight thiophene can make a perfect paradigm of windmill-type monogrid (WG). WG has the extension direction with a star radiative mode, especially WG4 with four arms being perpendicular to each other4 that has the same shape with unit on the ancient Chinese window. Diamond-type (DG) can be designed by the introduction of spirofluorenes with bilateral extension of two vertical double-arms. If four cross-shape spirobifluorenes are introduced into one closed molecular polygon with the 2,2’-linkage modes, the Tic-tac-toe-type grid (TG, #) can get access into perfectly square shape with at least eight arms to extend in four directions.5 Nanogrids require both biphenyl and sp3 carbon to attend the closure backbone of molecular polygon. As a result, nanogrids are different from cycloparaphene- based nanoring and most macrocycles such as calix[n]arenes as well as pillararenes. The intrinsic criteria of nanogrids are the characteristics of direction extensibility and expendability by means of well-defined edges/vertices. The value of fluorene is not only the unique synthon for flexible construction of nanogrids, but also facilitates the powerful and simple chemistry of Frediel-Crafts Gridization (FCG) owing to the features of reversibility, C—H activation and metal free, occurring at room temperature that is more advantageous over the Suzuki gridization. Various grid synthons of two AmBn and Am+Bn types were designed to give the LG, DHG, WG and DG structures, where A is the abbreviation of alcohol to represent –OH groups and B is an abbreviation of benzeniod to represent electrophilic arenes, Trans (RRS/ SSR) -triangle windmill-typed grid stereoisomer was confirmed by single-crystalline diffraction analysis.4 Half-gridarene was realized by fused fluorenes via the superelectrophilic gridization with the trans-selectivity.6 Theoretical calculation exhibited the #-shaped grid molecules with lower reorganization energy and strain energy.5 From the application point of view, DA grid has been designed for ion-electron-coupling memristors7 and WG for charge-trapping grid memory. Grid fluorenes offer the paradigm of carbozale, cyclopentathiophene, diazafluorenes, sillafluorene and fused structures that can be regarded as the category of fluoreniod derivatives. By means of the absolute advantages of well-defined edges and extendable vertices in monogrids, organic grid molecules can easily enter into all the formats of molecular matter, such as oligomer and polymer, dendrimer, framework, 3D cage, catenane and rotaxene as well as other chemical paradigms. After the fused digrid, the multigrid of prism was reported via one-pot nanosynthesis of FCG with the A2+B3 type (Figure 2d).8 LGs as the nanomonomers were introduced into soluble nanopolymers with either fully pi-conjugated or pi-interrupted modes.9 Fully conjugated polygrid exhibits the excellent morphological stability and blue emitters. Organic nanogrids are a huge molecular family that independently differ from all the molecular ontologies. Electro-active gridarene-based nanoscafolds would update organic and molecular electronics by means of the unprecedented nanoscale feature. Nanopolygrids would be transformed into high-performance advanced materials with the dual merits of the polymer and CNT without nanocomposite. Organic nanogrids possess installability, extensibility and scalability that offer the huge potential in terms of molecular window, molecular integration and molecular circuit. They would become the robust nanobridge to link between molecular and mesoscale world for intellibots. Although C—X gridization was made breakthrough with the covalent nanosynthesis, a dozen of challenges still exist in terms of high yield and stereo-selectivity, fluoreniod gridarenes as well as their nano-architectures (Figure 3). Among them, the Matryoshka-type grid (meta-grid, MG) is one key hierarchal and cross-scale molecular window. Besides the innovation of structures, gridization effect on ionic-to-electronic process should be another vital challenge from grid materials. Ultimately, the grand challenge on the road to organic intelligence is the molecular integration of various functons for the target of the Grid Fluorenoid IntelliBots (GFIB). Nanotechnology ; Chemistry ; Commercialization ; Manifesto ; Organic electronics ; Robot ; Artificial intelligence ; Computer science ; Electrical engineering ; Engineering ; Materials science Luminescence and Fluorescent Materials ; Advanced Memory and Neural Computing ; Machine Learning in Materials Science