Exploitation of room temperature (RT) photochromism and photomagnetism to induce single-molecule magnet (SMM) behavior has potential applications toward optical switches and magnetic memories, and remains a tremendous challenge in the development of new bulk magnets. Herein, a series of chain complexes [Ln 3 (H−HEDP) , and Y (QDU-1(Y)); HEDP = hydroxyethylidene diphosphonate; TPT = 2,4,6-tri(4-pyridyl)-1,3,5-triazine) were synthesized by solvothermal reactions. All the compounds exhibited reversible photochromic and photomagnetic behaviors via UV light irradiation at RT, induced by the photogenerated radicals via a photoinduced electron transfer (PET) mechanism. More importantly, the PET process induced significant variations in magnetic interactions for the Dy(III) congener. Strong ferromagnetic coupling with remarkably slow magnetic relaxation without applied dc fields was observed between Dy III ions and photogenerated O • radicals, showing SMM behavior after RT illumination. For the first time, we observed the reversible RT photochromism and photomagnetism in the lanthanide-based materials. This work realized the radicals-actuated on/off SMM behavior via RT light irradiation, providing a new strategy for constructing the lightinduced SMMs.

Using the pillar-layer strategy, two isomorphic crystalline coordination compounds with obvious photochromic and photomagnetic behaviors actuated by nonphotochromic ligands were synthesized.

A series of platinum(II) terpyridyl alkynyl complexes, [Pt{4'-(4-R1-C6H4)terpy}(C[triple chemical bond]C-C6H4-R(2)-4)]ClO4 (terpy=2,2':6',2''-terpyridyl; R1=R2=N(CH3)2 (1); R1=N(CH3)2, R2=N-[15]monoazacrown-5 (2); R1=CH3, R2=N(CH3)2 (3); R1=N(CH3)2, R2=H (4); R1=CH3, R2=H (5)), has been synthesized and the photophysical properties of the complexes have been examined through measurement of their UV/Vis absorption spectra, photoluminescence spectra, and transient absorptions. Complex 3 shows a lowest-energy absorption corresponding to a ligand-to-ligand charge-transfer (LLCT) transition from the acetylide to the terpyridyl ligand, whereas 4 shows an intraligand charge-transfer (ILCT) transition from the pi orbital of the 4'-phenyl group to the pi* orbital of the terpyridyl. Upon protonation of the amino groups in 3 and 4, their lowest-energy excited states are switched to dpi(Pt)-->pi*(terpy) metal-to-ligand charge-transfer (MLCT) states. The lowest-energy absorption for 1 and 2 may be attributed to an LLCT transition from the acetylide to the terpyridyl. Upon addition of an acid to a solution of 1 or 2, the amino group on the acetylide is protonated first, followed by the amino group on the terpyridyl. Thus, the lowest excited state of 1 and 2 can be successively switched from the LLCT state to the ILCT state and then to the MLCT state by controlling the amount of the acid added. Such switches in the excited state are fully reversible upon subsequent addition of a base to the solution. Sequential addition of alkali metal or alkaline earth metal ions and then an acid to a solution of 2 also leads to switching of its lowest excited state from the LLCT state, first to the ILCT state and then to the MLCT state. All of the complexes exhibit a transient absorption of the terpyridyl anion radical, which is present in all of the LLCT, ILCT, and MLCT states. However, the shape of the transient absorption spectrum depends on both the substitution pattern on the terpyridyl moiety and the nature of the excited state.

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Room-temperature ionic liquids (RTILs) have recently received a great deal of attention as alternative reaction media.[1] Numerous catalytic reactions have proven feasible in a variety of ionic liquids, with many reactions displaying enhanced reactivities and selectivities, and some of which were not possible in common organic solvents.[2] Furthermore, RTILs have served as a promising means to immobilize a catalyst, therefore facilitating product isolation and offering an opportunity to reuse the catalyst. However, the use of RTILs in asymmetric catalytic reactions is still limited. [1f,g, 2f, 3] The recycling and reuse of chiral catalysts in ionic liquids have often been problematic because of the instability and/or leaching of the catalysts. From a practical standpoint, development of highly effective and recyclable catalysts in ionic liquids for use in asymmetric hydrogenation remains a challenge: in particular for heteroaromatic substrates which are difficult to hydrogenate.Although a variety of chiral Rh, Ru, and Ir complexes have been efficient and enantioselective reagents for the hydrogenation of prochiral olefins, ketones, and imines, [4] most of these catalysts failed to give satisfactory results in the asymmetric hydrogenation of heteroaromatic compounds.[5] A few successful examples for the asymmetric hydrogenation of quinolines have recently been reported. [6] However, all catalysts for such reactions have at least one phosphine ligand around the metal center and are often air sensitive.[7] From the viewpoints of both scientific interest and practical application, it is highly desirable to develop recyclable and phosphine-free chiral catalysts for the highly enantioselective hydrogenation of quinolines. Few examples of phosphine-free homogeneous catalysts capable of activating molecular hydrogen have been reported. [8] Recently, Noyori and co-workers reported that chiral h 6 -arene/Ntosylethylenediamine-Ru II complexes (which are known as excellent catalysts for asymmetric transfer hydrogenation, for example Ru/Ts-dpen) can be used for the asymmetric hydrogenation of prochiral ketones under slightly acidic conditions.[9] Inspired by this important breakthrough and following our continued pursuit of developing effective and environmentally benign catalyst systems for asymmetric hydrogenations, [10] herein we report a practical and efficient catalyst system of Ru/Ts-dpen in [BMIM]PF 6 (BMIM = 1-nbutyl-3-methylimidazolium) for the enantioselective hydrogenation of quinolines (Scheme 1).We have found that quinoline substrates could be efficiently hydrogenated to give 1,2,3,4-tetrahydroquinolines with excellent enantioselectivities (up to 99 % ee) in neat ionic liquid without the need for additives. Furthermore, the catalyst, which was highly stable in ionic liquid and maintained the same activity even after exposure to air for 30 days, could be easily recycled.Considering that methanol has been successfully used in the asymmetric hydrogenation of ketones by Noyori and coworkers, [9] we first examined ...

Two classical metal clusters, Cu I 4 I 4 and Cu I 6 S 6 , are introduced as functional connecting nodes to construct a novel multi-metal-cluster MOF [(Cu I 4 1) that incorporate their inherent luminescent properties, induced by their respective metal-metal interactions. These two distinct clusters are combined together for the first time to perform as functional luminophores that display unusual dual emission with both thermochromic luminescence and near-infrared (NIR) character.

No abstract

Metal−organic frameworks (MOFs), as an emerging hybrid material, have been well explored in numerous areas such as adsorption, separation, catalysis, magnetism, photoluminescence, etc. Recently, the intermarriage of MOFs and photochromism gives birth to a new category of hybrid materials with multiple photoresponsive functionality. Hitherto, most of photochromic MOFs are constructed from photoactive units like pyridinium-derivatives. We, herein, propose a mixed-ligand strategy for the fabrication of photochromic MOFs driven by electron transfer (ET) between nonphotoactive units, that is, the coordinative linkage of electron-rich carboxylate as electron donors (EDs) and conjugated pyridine ligands as electron acceptors (EAs) via the framework approach.