The potential of palladacycles: more than just precatalysts

The understanding of the dual fluorescence of certain aromatic systems has greatly advanced in recent years. The accompanying large charge separation has been shown to be linked to a twisted (or small overlap) arrangement of the chromophores. Recent theoretical models are able to describe the excited-state twisting of both single bonds (TICT compounds) and double bonds (olefins) in a unified picture. These models can help to elucidate the photophysical behavior of many organic, inorganic, and biologically relevant compounds, and their application to laser dyes and fluorescent probes provides a route to new “tailor-made” fluorescent materials. Applied to the primary processes of vision and photosynthesis, these models can lead to a deeper understanding of basic photobiological processes.

Charge Separation in Excited States of Decoupled Systems—TICT Compounds and Implications Regarding the Development of New Laser Dyes and the Primary Process of Vision and Photosynthesis

Light-Emitting Self-Assembled Materials Based on d(8) and d(10) Transition Metal Complexes.

The use of photoinitiated polymerization is continuously growing in industry as reflected by the large number of applications in not only conventional areas such as coatings, inks, and adhesives but also high-tech domains, optoelectronics, laser imaging, stereolithography, and nanotechnology. In this Perspective, the latest developments in photoinitiating systems for free radical and cationic polymerizations are presented. The potential use of photochemical methods for step-growth polymerization is also highlighted. The goal is, furthermore, to show approaches to overcome problems associated with the efficiency, wavelength flexibility, and environmental and safety issues in all photoinitiating systems for different modes of activation. Much progress has been made in the past 10 years in the preparation of complex and nano-structured macromolecules by using photoinitiated polymerizations. Thus, the new and emerging applications of photoinitiated polymerizations in the field of biomaterials, surface modific...

Photoinitiated Polymerization: Advances, Challenges, and Opportunities

Spectroscopic and photochemical properties of d10 metal complexes

Study of intramolecular sensitization and other excited-state pathways in orthometalated azobenzene complexes of palladium(II)

It is shown that visible light irradiation of trans-[Cr(NH 3 ) 2 (NCS) 4 ] - dissolved in ethyl α-cyanoacrylate initiates anionic polymerization. The results suggest that ligand field excitation of judiciously selected transition metal complexes represents a promising strategy for the controlled release of anionic initiators.

A novel strategy for photoinitiated anionic polymerization

Photocalorimetry. 6. Enthalpies of isomerization of norbornadiene and of substituted norbornadienes to corresponding quadricyclenes

The valence isomerization of norbornadiene to quadricyclene can be photosensitized with high quantum efficiency by certain copper(I)-phosphine compounds. Sensitization yields in the presence of Cu(PPh/sub 3/)/sub 2/BH/sub 4/ and Cu(PPh/sub 2/Me)/sub 3/BH/sub 4/ attain limiting values of 0.76 and 0.54, respectively, at high norbornadiene concentrations. In contrast, Cu(diphos)BH/sub 4/ (diphos is 1,2-bis(diphenylphosphino)ethane), which contains a bidentate phosphine ligand, is decidely less effective. The mechanism of sensitization by these copper(I)-phosphine compounds is fundamentally different from that exhibited by simple cuprous salts in that no ground-state coordination to the metal center occurs. A pathway involving the bimolecular interaction of the photoexcited Cu(I) compound with a ground-state norbornadiene molecule is better able to accommodate the available data. Electronic absorption and emission studies reveal some interesting differences between the spectral properties of effective vs. noneffective sensitizers.

Photobehavior of copper(I) compounds. Role of copper(I)-phosphine compounds in the photosensitized valence isomerization of norbornadiene

A study was made of the norbornadiene (NBD) to quadricyclene (Q) conversion in the presence of Cu(P(CH/sub 6/H/sub 5/)/sub 3/)/sub 2/BH/sub 4/, Cu(P(C/sub 6/H/sub 5/)/sub 2/(CH/sub 3/))/sub 3/BH/sub 4/, and Cu(diphos)BH/sub 4/ (diphos is 1,2-bis(diphenyl-phosphino)ethane). The first two compounds were approximately 60 to 90 times more effective than the latter compound in sensitizing the production of Q. Furthermore, the mechanism of sensitization appears to be fundamentally different from that involving CuX salts (where X is Cl, Br, I, or C/sub 2/H/sub 3/O/sub 2/). (JSR)

Paul A. Grutsch

Papers

Study of intramolecular sensitization and other excited-state pathways in orthometalated azobenzene complexes of palladium(II)

A novel strategy for photoinitiated anionic polymerization

Photocalorimetry. 6. Enthalpies of isomerization of norbornadiene and of substituted norbornadienes to corresponding quadricyclenes

Photobehavior of copper(I) compounds. Role of copper(I)-phosphine compounds in the photosensitized valence isomerization of norbornadiene

Use of copper(I) phosphine compounds to photosensitize the valence isomerization of norbornadiene