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Please release me: The heat generated when metal nanoparticles absorb light results in a significant increase in the temperature of the environment around the particles and is used to selectively break bonds within a molecular system anchored to the nanoparticle surface (see picture). This process represents an advantageous and more universal method to deliver chemicals locally, while avoiding excessive tissue damage.

The guanidinato- or amidinato-bridged diarsenes [As2{mu-(ArN)2CR}2] (Ar = C6H3Pri2-2,6; R = N(C6H11)2, NPri2, or But) have been prepared by reduction of the corresponding As(III) precursors, [Cl2As{kappa2-N,N'-(ArN)2CR}]. Theoretical studies suggest that the As-As bonds of the dimers have significant double-bond character, the sigma and pi components of which are derived mainly from As p orbital overlaps.

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A novel fulvene-type bidentate ligand 1 has been synthesized by an aroylation reaction of cyclohexyl-substituted cyclopentadienyl anions. Compound 1 crystallizes in the triclinic space group P(-)1, with a = 7.0419(5) A, b = 11.9360(8) A, c = 15.6470(11) A, alpha = 85.1440(10) degrees, beta = 78.1140(10) degrees, gamma = 74.5360(10) degrees, V = 1239.76(15) A(3), and Z = 2. The coordination chemistry of 1 was investigated, and a novel Ag-containing coordination polymer (2), linked by both Ag-heteroatom and Ag-carbon interactions, has been synthesized. The coordination polymer has been fully characterized by infrared spectroscopy, elemental analysis, and single-crystal X-ray diffraction. Compound 2 crystallizes in the triclinic space group P(-)1, with a = 7.1654(5) A, b = 15.7277(11) A, c = 18.8157(13) A, alpha = 73.5150(10) degrees, beta = 89.0410(10) degrees, gamma = 89.0970(10) degrees, V = 1355.19(14) A(3), and Z = 2. The solid-state structure of 2 features a one-dimensional double-chain motif. These double chains are in turn cross-linked to each other via strong interchain O-H...O hydrogen bonds, forming a novel two-dimensional network with remarkably large cavities (effective cross section of ca. 21 x 15 A) that are occupied by benzene guest molecules. Both compounds 1 and 2 are luminescent in the solid state, and a large blue-shift in the emission between the free ligand 1 and the ligand incorporated into complex 2 is observed.

New methods for the spatially and temporally controlled delivery of chemical and/or biochemical species using lowenergy visible light offers greater opportunities in photodynamic therapy, [1] chemical synthesis, [2] and photolithography. [3] The fact that designer metal nanoparticles absorb light of specific frequencies (at their plasmon resonance) and efficiently convert it into heat (through the photothermal effect) is a particularly appealing phenomenon that has been effectively used to trigger cell death [4] and melt ice [5] within the vicinity of the nanoparticles. However, to date, the heat generated when visible light is absorbed by such structures has not been used to initiate delivery events. This is surprising, as this technique would provide a convenient and general method to break chemical bonds and release biologically relevant payloads from the nanoparticle surfaces. Both detrimental (poisonous) and beneficial (therapeutic) agents could be released on command by using such a universal method.We recently set out to develop a new method to harness the local heat that dissipates from the nanoparticles when they are stimulated with visible light, in order to trigger thermally activated bond-breaking reactions close to the nanoparticle surfaces without significantly increasing the temperature of the surrounding environment. This approach has a benefit over others in that specific agents can be delivered to a cell without damaging it. Herein, we describe how we can trigger the release of a fluorescent dye from coreshell nanoparticles as the first illustration of a generalized approach to photothermal release.We chose the retro-Diels-Alder reaction to demonstrate our new release method because the temperature at which it is activated can be easily tuned by modifying the structure of the two chemical components (the diene and dienophile). [6] This cycloaddition reaction is particularly well-suited for surface-localized chemistry and has been used to selectively decorate [7] and control nanoparticle aggregation [8] by directly applying heat to suspensions of nanoparticles. The photothermal effect has yet to be taken advantage of in this context. We identified a specific retro-Diels-Alder reaction (shown in the substructure in Figure 1 a). Our choice was based on the fact that the bond-breaking reaction of 7-oxa-bicyclo-[2.2.1]hept-5-ene-2,3-dicarboxylic imide to release a furan and a maleimide component barely occurs at room temperature but proceeds above 60 8C. Model studies on both the endo and exo isomers of the depicted bicyclic system suggest that, as expected, the use of the former isomer is advantageous [9][10][11] since is cleanly converts into its two components at Figure 1. a) Release of the fluorescein dye from the surface of a silicagold core-shell nanoparticle by using the photothermal effect to induce the retro-Diels-Alder reaction of an anchored 7-oxa-bicyclo-[2.2.1]hept-5-ene-2,3-dicarboxylic imide derivative. UV/Vis absorption spectra of aqueous dispersions with TEM images of each type of pa...

Reactions of lithium salts of the bulky guanidinate and phosphaguanidinate ligands, [ArNC(ER 2 )NAr] À (ER 2 = NPr i 2 (Priso À ), cis-NC 5 H 8 Me 2 -2,6 (Pipiso À ) or P(C 6 H 11 ) 2 (PGiso À ); Ar = C 6 H 3 Pr i 2 -2,6), with group 13 metal(I) halides have been carried out. All reactions with TlBr led to monomeric thallium(I) complexes, [Tl{ArNC(ER 2 )NAr}], in which the ligand chelates the metal in an N,arene-fashion. The reactions with InCl led to mixed results and the isolation of the dimeric indium(II) complexes, [{InCl(Priso)} 2 ] and [{InCl(Pipiso)} 2 ], and the monomeric indium(I) species, [In(Pipiso)] and [In(PGiso)]. The ligands of the latter two complexes exhibit differing coordination modes in the solid state, namely N,N 0 -chelating and N,arene-chelating, respectively. The reactions with ''GaI'' were less successful and gave only low yields of the poorly characterised gallium(II) complexes, [{GaI(Priso)} 2 ] and [{GaI(Pipiso)} 2 ]. This study has shown that the related ligand, [ArNC{N(C 6 H 11 ) 2 }NAr] À (Giso À ) is superior for the stabilisation of group 13 metal(I) complexes. The oxidative additions of I 2 or SiMe 3 I to one such complex, [Ga(Giso)], yielded the gallium(III) compounds, [GaI 2 (Giso)] and [GaI(SiMe 3 )(Giso)].