Regioselective Photochemical Cycloaddition Reactions of Diolefinic Ligands in Coordination Polymers

Abstract

The pure diolefinic ligand 1,4-bis(pyridin-4-yl)-1,3butadiene (bpbde) is photostable in the crystalline state. With the assistance of coordination-driven metal-organic assemblies, the photoreactivity of this diolefinic ligand can be significantly enhanced. Ah ydrothermal reactiono fb pbde with Cd(NO 3 ) 2 ·4 H 2 Oa nd the auxiliary ligand adipic acid resulted in the formation of at wo-dimensional photoreactive coordination polymer (CP), [Cd(adipate)(bpbde)] n (1). When the aliphatic carboxylica cid was replaced by pimelic acid, another photoreactive CP [Cd(pimelate)(bpbde)] n (2)w ith a three-dimensional framework waso btained. With irradiation of 365 nm UV light, the bpbde ligands in crystalline 1 and 2 underwent ar egioselective photochemical [2+ +2] cycloaddition reaction and convertedt o3 ,4,7,8-tetra(pyridin-4-yl)tricyclo[4.2.0.0 2,5 ]octane (tptco)a nd 1,3-bis(pyridin-4-yl)-2,4-bis(2-(pyridin-4-yl)vinyl)cyclobutane (bpbpvcb), respectively.T he resultsp rovide an interesting insight into the rational design of highly regio-or stereoselective photocatalytic reactions for the formation of special organic molecules.

Properties of Aliphatic Ligand-Based Metal–Organic Frameworks

“…The SCXRD for the crystal after the irradiation revealed a partial dimerization (Figure 12) which was thus driven by the flexibility of the aliphatic allylmalonate ligand. Despite this, it would be fair to note that in [76] and some other works [77][78][79][80], the ligand flexibility is evident to be not strictly required for the successful carrying out of UV-induced reactions in MOFs.…”

Two-Dimensional Metal-Organic Framework Materials: Synthesis, Structures, Properties and Applications

“…In the photoreactive 2D MOF [Cd 2 (adipate) 2 (bpbde) 2 ] (bpbde = 1,4-bis­(pyridin-4-yl)-1,3-butadiene), the adipate ligand form the typical dinuclear-based repeating unit by bridging two Cd­(II) atoms and chelating each Cd­(II) atom . The conformation of the −CH 2 – chains dictate the formation of a 1D chain comprising loops or rings similar to the angular 1,3-bdc ligand described above.…”

“…2D to 2D SCSC structural transformation in [Cd 2 (adipate) 2 (bpbde) 2 ] showing 52.7% photoreaction. Adapted with permission from ref . Copyright 2014 John Wiley & Sons.…”

Photoreactive Crystal of a Copper(I) Coordination Compound with a Cinnamaldehyde Derivative

“…If the initial geometry of the system is not perfect but we anticipate the possibility of a photoreaction, a larger space is preferable (createsan opportunity for molecules to shift around). The design of photoactive systems and control of the reactions in the solid state are some of the main goals of crystal engineering. , Various approaches related to formation of the intermolecular interactions such as halogen , and hydrogen bonds, , π···π stacking, and coordination bonds − are applied to control the packing of CC bonds suitable for the reaction in the solid state. In the last approach, the directional properties of the ions are the driving forces for orientation for a regiospecific photoinduced reaction.…”