Toward Covalently Linked Organic Networks:  Model Studies and Connector Syntheses

Abstract

A model 1-naphthoic acid bearing a peri-positioned cinnamic acid residue crystallizes as a closed H-bonded dimer. Irradiation of this crystalline solid provides an α-truxillate-type cyclobutane photodimer in quantitative yield. Further synthesis studies have led to more highly functionalized naphthoic/cinnamic acid species capable of (pseudo)centrosymmetric attachment to polyvalent hubs. This system demonstrates the feasibility of designing a covalent molecular connector whose orientation is encoded by its H-bonding pattern.

Template effects and supramolecular control of photoreactions in solution

“…Photoinduced cycloaddition reactions involving conjugated alkenes are particularly interesting for investigating supramolecular templates in homogeneous and heterogeneous environments. The availability of relatively precise data on the prerequisites of the spatial arrangement of the reactants owing to solid-state photodimerization data [32][33][34][35] makes it possible to formulate useful supramolecular structure-photoactivity predictions. It is generally admitted that the participating p-orbitals should be in near contact, i.e.…”

“…Later, Feldman and co-workers used a naphthalene scaffold to orient cinnamate chromophores and quantitatively steer their photodimerization towards the a-truxillate photodimer. 32 Fig. 1 Schematic representation of a process involving photochemical capture of a non-covalent architecture assembled around a template (filled circle).…”

Photocapture of dynamic hydrogen‐bonded assemblies

“…More recently, Bach and co-workers have used intermolecular hydrogen bonding to exert stereochemical control of photoinduced cycloaddition reactions [6]. Along similar lines Feldman et al [7] constructed hydrogen-bonded assemblies in the solid state. Their results indicated the near quantitative formation of the α-truxillate (see Figure 3) in the solid state with an extremely low photoreactivity in solution.…”

Intraannular photoreactions in pseudo-geminally substituted [2.2]paracyclophanes

“…Unlike photochemistry in homogeneous solution, this often leads to highly selective formation of the photoproducts. Schmidt coined the term “topochemical principle” or “topochemistry” for (non)reactivity determined by a limiting distance between the reactive groups [ 2 – 4 ]. Although the model found widespread acceptance, many exceptions to the concept were known from the very beginning [ 5 ].…”