Construction of Photoreactive Chiral Metal–Organic Frameworks and Their [2 + 2] Photocycloaddition Reactions

Abstract

Chiral metal–organic frameworks (CMOFs) and solid-state [2 + 2] photocyclization have been explored as independent areas in crystal engineering. We herein report the photoreactive CMOFs that undergo a [2 + 2] photocycloaddition reaction for the first time. Through the incorporation of a dipyridyl olefin ligand, 1,4-bis­[2-(4-pyridyl)­ethenyl]­benzene, and d-camphoric acid or l-camphoric acid, we constructed a pair of homochiral Zn­(II) CMOFs (d-1 or l-1) with a two-dimensional sql topology via a two-step procedure to avoid racemization. Both d-1 and l-1 were photoinert due to the large olefin bond separation. The removal of the solvent molecules between layers enabled them (d-1a and l-1a) to undergo [2 + 2] cycloaddition reactions; d-1a is more reactive (70%) than l-1a (20%) probably due to proper desolvation-induced rearrangement. The photoluminescence properties are also discussed. This work presents a new perspective on photoreactive homochiral network materials with diverse topologies and applications.

Construction of olefinic coordination polymer single crystal platforms: precise organic synthesis, in situ exploration of reaction mechanisms and beyond

“…have reported examples of solid-state SCSC photodimerization reactions of L 16 pairs in various CPs, which provided single crystal platforms for the organic synthesis of 1,3-bis(4-pyridyl)-2,4-bis(4-(2-(4-pyridyl)-vinyl)phenyl)cyclobutane (OP 19 ), tetrakis(4-pyridyl)-1,2,9,10-diethano[2,2]paracyclophane (OP 20 ) and 4,4′-(3,4-bis(4-(( E )-2-(pyridin-4-yl)vinyl)-phenyl)cyclobutane-1,2-diyl)dipyridine (OP 21 ) dimers. 114–117 By the self-assembly of Zn( ii ) with L 16 and 5-sulfoisophthalic acid (H 3 A 29 ), a photoreactive diolefinic CP of [{Zn 4 (μ 3 -OH) 2 (A 29 ) 2 (L 16 ) 2 }·4H 2 O] n ( 76 ) was synthesized for [2+2] cycloaddition. 114 In 76 , there were two types of alignments for L 16 pairs, i.e.…”

“…The synthesis of dimer OP 20 was also achieved by Vittal, Park et al using similar single crystal platforms of CPs. 115,116 In [{Zn 2 (L 16 ) 2 (A 8 ) 2 }·2DMF·2H 2 O·0.5DMSO] n ( 78 ), [{Zn 2 (L 16 ) 2 (A 8 ) 2 }·2DMA·2H 2 O] n ( 79 ) and [{Zn 2 (L 16 ) 2 ( d -A 31 ) 2 }·6DMA] n ( 80 , H 2 d -A 31 : d -camphoric acid), the in-phase arrangement of L 16 pairs promoted the generation of OP 20 upon exposure to light and light-heat stimuli. When we replaced H 2 A 30 with 4,4′-(ethene-1,2-diyl)dibenzoic acid (H 2 A 32 ), we obtained the CP [Cd 2 (A 32 ) 2 (L 16 ) 2 ] n ( 81 ) in the presence of Cd( ii ) and L 16 .…”

Photocycloaddition of Zero-Dimensional Metal Halide Hybrids with Reversible Photochromism

“…Since [2 + 2] photocycloaddition brings about great variation in lattice strain and conjugation of π electrons, it has been widely employed in the fields of photomechanical motions and optoelectronic devices including optical writing and data storage without any physical contact. − In principle, parallelly aligned olefinic bonds within less than 4.2 Å can undergo [2 + 2] photocycloaddition according to Schmidt’s criteria. − To satisfy this prerequisite, metal–organic frameworks (MOFs) and coordination polymers (CPs) with wide structural tunability and good designability are often designed to bring olefin group into the required alignment or incorporate olefins in the confined space. ,− …”

Solid-State Photodimerization Reaction with Photosalient Effect and Photophysical and Electrochemical Properties of N-Methylated 1-Naphthylvinyl-4-Quinoline

“…Template-controlled solid-state photoreactivity of two CC bonds has been well investigated in the past in cocrystals, organic salts, coordination complexes, and coordination polymers and metal–organic frameworks. − Wherein, a pair of olefin molecules are brought into parallel orientation within a distance <4.2 Å between CC bonds (Schmidt postulate) by utilizing directional intermolecular inactions such as hydrogen bonding, − charge-assisted hydrogen bonding, − halogen bonding, − and coordination bonding. − By exploiting such interactions, unsymmetric olefins can be stacked parallel in two ways, head-to-head (HH) and head-to-tail (HT), leading to the possibility of formation of two structural isomers of the cyclobutane products upon photochemical reaction. − Owing to the presence of the prevailing cation–π interaction in organic salts, most of the unsymmetric olefins stack in a head-to-tail manner and thus produce the HT-dimer regioselectively. − ,− Pyridyl-based olefins have been investigated as their protonated salts with various anions. N -alkylated pyridinium-substituted olefin compounds are rarely explored in recent times. − …”