Nitro–Nitrito Photoisomerization of Cationic Platinum(II) Complexes in the Solid State: Reactivity in Polymorphic Crystals and Glassy State

Abstract

Nitro-nitrito isomerization is a well-known photoreaction exhibited by metal complexes in the solid state. We previously reported that the isomerization ratio in the salts of a cationic platinum(II) nitrito complex [Pt(L)(NO2)] + (L = N 1 -(2-(dimethylamino)ethyl)-N 2 ,N 2 -dimethyl-N 1pentyl-1,2-ethanediamine) is correlated to the reaction cavity surrounding the nitrito ligand. In this study, to further elucidate the effect of the packing structure on the reaction, we investigated the photoisomerization of the same cation in different packing environments. The salt of the cationic complex with the PF6 anion gave three polymorphs (-, -, and -forms) and a pseudopolymorph (form, acetonitrile solvate), of which the -form is formed from the -form upon desorption of acetonitrile. These polymorphs exhibited 36-100% conversions at 180 K depending on the reaction cavity. In addition, the -form exhibited a space group change upon photoirradiation. The salt with the (CF3SO2)2N − anion was an ionic liquid, taking both the crystalline and glassy states at low temperature.The crystalline state exhibited approximately 30% conversion at 100 K, whereas photoisomerization was not observed in its glassy state as investigated by IR spectroscopy. In these salts, less densely packed crystals deteriorated upon photoirradiation.Molecular structures, IR spectra, bond lengths and angles, and crystallographic parameters (PDF).

Exploring Photoswitchable Properties of Two Nitro Nickel(II) Complexes with (N,N,O)-Donor Ligands and Their Copper(II) Analogues

“…These are the cavity volume and the intermolecular interactions involving the ambidentate ligand. Indeed, it is essential to ensure the space necessary for the NO 2 group to undergo light-induced linkage isomerization. ,− , Naturally, not only the size of the cavity but also its shape are relevant so as to ensure the smallest possible changes in the unit cell upon the molecular transformation . Hence, the reaction cavity volumes were calculated for all examined crystal structures using the MERCURY software (with the rolling-probe method with a probe radius of 1.2 Å and a grid spacing of 0.1 Å) and analyzed.…”

“…Molecular switches triggered by UV–vis light may find wide applications in high-capacity storage devices, optoelectronics, medicine, as color-changing materials, etc. , Therefore, the importance of studies dedicated to the conscious design of new functional photoswitchable systems with the desired properties cannot be overestimated. − Transition-metal complexes in which the metal center is coordinated by molecular fragments that can exist in multiple isomeric forms are among the potential functional materials of this kind . Examples of ambidentate ligands known to display solid-state linkage isomerism include NO, , NO 2 , ,,− SO 2 , − SCN, and N 2. Transition-metal complexes containing nickel, ,,, cobalt, − iron, ruthenium, , osmium, palladium, or platinum − , centers are the most representative examples of such systems.…”

Advances in Diffraction Studies of Light-Induced Transient Species in Molecular Crystals and Selected Complementary Techniques

“…This allows examination of relatively shorterlived species, which would otherwise relax back to the ground state. Since these two methods do not require any specific and advanced experimental setups, they have been used extensively to study structural dynamics of a variety of systems, with particular emphasis on photo-switchable materials undergoing for example photoisomerization or reversible photolysis [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46].…”

Relating Excited States to the Dynamics of Macroscopic Strain in Photoresponsive Crystals

“…Complexes in which the NO 2 ligand coordinates to the metal ion via nitrogen are termed “nitro” isomers, whereas complexes in which NO 2 coordinates via oxygen are termed “nitrito” isomers (Scheme ). Detailed studies of the linkage nitro–nitrito isomerization in [Co­(III)­(NH 3 ) 5 NO 2 ]­Cl 2 were reported in the 20th century (summarized in refs and ) and were extended to studies of complexes of many other metals, including Pt, Ni, Ru, Fe, and others. − Similarly, linkage isomerization of complexes with other ligands, such as nitrosyl or SO 2 , has been explored, as have compounds comprising more than one nitro/nitrito-ligand. − …”