Communication pubs.acs.org/IC
Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX
Sunlight-Induced Topochemical Photodimerization and Switching of the Conductivity of a Metal−Organic Compound Basudeb Dutta,† Arka Dey,‡ Chittaranjan Sinha,§ Partha Pratim Ray,*,‡ and Mohammad Hedayetullah Mir*,† †
Department of Chemistry, Aliah University, New Town, Kolkata 700 156, India Department of Physics and §Department of Chemistry, Jadavpur University, Jadavpur, Kolkata 700 032, India
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S Supporting Information *
cyclobutane ring in a 1D chain could be cleaved back to form olefin by heating. This reversible reaction accompanied by switching of the conductivity leads to the development of an electronic device based on molecular switches. Compound 1 has been synthesized in the dark by the slow diffusion of 4-nvp in methanol and Hquin in ethanol into an aqueous solution of Cd(NO3)2·6H2O and triethylamine in water/methanol. However, compound 1′ can be synthesized by either exposing the reaction mixture to sunlight or keeping the crystals of 1 (obtained in the dark) in strong sunlight. Singlecrystal X-ray analysis reveals that compound 1 crystallizes in the monoclinic space group P1̅ with Z = 1. Each cadmium(II) center adopts a distorted octahedral coordination geometry, ligated to two chelating quin ligands in the equatorial plane and two 4-nvp ligands at the axial sites (Figure 1). In the solid-state structure, a
ABSTRACT: A metal−organic compound [Cd(quin)2(4-nvp)2] [1; Hquin = quinoline-2-carboxylic acid and 4-nvp = 4-(1-naphthylvinyl)pyridine] undergoes topochemical [2 + 2] cycloaddition by sunlight irradiation to generate a one-dimensional coordination polymer. This reaction is thermally reversible, and switching between two crystalline forms can be monitored by conductivity measurements.
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n recent years, solid-state reactions involving structural transformations receive considerable attention among the researchers working in the field of coordination polymers (CPs).1−5 This is attributed to the involvement of a solvent-free simple synthetic procedure and the formation of product that may otherwise be difficult to obtain by a conventional route. Of the various solid-state reactions, photochemical [2 + 2] photodimerization, by which a stereoseletive cyclobutane ring is formed in photoactive organic as well as coordination compounds, is particularly interesting.6−11 More recently, reversible [2 + 2] photodimerization involving the formation and cleavage of a cyclobutane ring has currently emerged as a new synthetic route for the fabrication of molecular switching, optical recording and storage devices, sensors, and photochemical actuators.12−15 However, reversible photodimerization reactions accompanied by switching of the conductivity for the fabrication of electronic and optoelectronic devices are still scarce.16,17 Most of the photochemical [2 + 2] cycloaddition reactions have been carried out using harmful UV radiation. On the basis of green synthesis, dimerization reactions using solar radiation have rarely been explored.18,19 Herein, we report the synthesis of a monomeric metal−organic compound, [Cd(quin)2(4-nvp)2] [1; Hquin = quinoline-2-carboxylic acid and 4-nvp = 4-(1naphthylvinyl)pyridine; CCDC 1868133], which undergoes sunlight-induced topochemical [2 + 2] cycloaddition and generates a one-dimensional (1D) CP via crystal-to-crystal transformation. However, the structure of the dimerized product [Cd(quin)2(rctt-4-pncb)]n [1′; rctt-4-pncb = 1,3-bis(4′-pyridyl)-2,4-bis(naphthyl)cyclobutane; CCDC 1868134] has been confirmed by a single-crystal X-ray crystallographic experiment of the crystal obtained by keeping the reactor in sunlight. Because of this structural change, there has been a significant effect on the electrical property of the material. The conductivity becomes notably low after dimerization. Interestingly, a © XXXX American Chemical Society
Figure 1. X-ray crystal structure of compound 1 showing the alignment of 4-nvp ligands. Hydrogen atoms are not shown for clarity.
pair of 4-nvp ligands from two adjacent moieties produces a head-to-tail arrangement with a distance between the centers of two CC bonds of 4.094 Å (Figure 1), which is highly favorable for dimerization according to Schmidt’s criteria (
