Alkynyl complexes, properties

The chemistry of metal complexes featuring alkyne and alkynyl (acetylide) ligands has been an area of immense interest for decades. Even the simplest examples of these, the mononuclear metal acetylide complexes L MC=CR, are now so numerous and the extent of their reaction chemistry is so diverse as to defy efforts at a comprehensive review. " The utility of these complexes is well documented. Some metal alkynyl complexes have been used as intermediates in preparative organic chemistry and together with derived polymeric materials, many have useful physical properties including liquid crystallinity and nonlinear optical behaviour. The structural properties of the M—C=C moiety have been used in the construction of remarkable supramolecular architectures based upon squares, boxes, and other geometries. ... 

Platinum complexes (continued) with aryls, thallium adducts, 3, 399 with bis(alkynyl), NLO properties, 12, 125 with bisalkynyl copper complexes, 2, 182-186 with bis(3,5-dichloro-2,4,6-trifluorophenyl), 8, 483 and C-F bond activation, 1, 743 in C-H bond alkenylations, 10, 225 in C-H bond electrophilic activation studies, 1, 707 with chromium, 5, 312 with copper, 2, 168 cyclometallated, for OLEDs, 12, 145 in diyne carbometallations, 10, 351-352 in ene-yne metathesis, 11, 273 in enyne skeletal reorganization, 11, 289 heteronuclear Pt isocyanides, 8, 431 inside metallodendrimers, 12, 400 kinetic studies, 1, 531 on metallodendrimer surfaces, 12, 391 mononuclear Pt(II) isocyanides, 8, 428 mononuclear Pt(0) isocyanides, 8, 424 overview, 8, 405-444 d -cP oxidative addition, PHIP, 1, 436 polynuclear Pt isocyanides, 8, 431 polynuclear Pt(0) isocyanides, 8, 425 Pt(I) isocyanides, 8, 425 Pt(IV) isocyanides, 8, 430... 

In the fields of organometallic polymer see Polymer) chemistry , in which complexes may have particularly interesting physical properties (liquid crystallinity, optical nonlinearity see Nonlinear Optical Materials), etc.), or of molecular electronics , metal alkynyl complexes play a significant role. These areas have been the subject of recent reviews, thus only a brief overview of methods to prepare iron alkynes will be given here. Liu has also recently reviewed the cyclization chemistry of alkynyl organometaUics, including those of iron. ... 

A series of luminescent mercury(II) bis(alkynyl) complexes containing oligothiophenes have been synthesized by Wong via direct merciuation of the corresponding alkynes (see equation S). Most importantly, the optical properties of these species have been found to be easily tuned by modifying the... 

The copper(I) alkynyls displayed rich photochemistry and particularly strong photoreducing properties. The transient absorption difference spectrum of [Cu3(dppm)3(/X3-) -C=CPh)2]+ and the electron acceptor 4-(methoxycarbonyl)-A-methylpyridinium ion showed an intense characteristic pyridinyl radical absorption band at ca. 400 nm. An additional broad near-infrared absorption band was also observed and it was assigned as an intervalence-transfer transition of the mixed-valence transient species [Cu Cu Cu (dppm)3(/x3- -C=CPh)2] +. The interesting photophysical and photochemical properties of other copper(I) alkynyl complexes such as [Cu(BTA)(hfac)], 2 [Cui6(hfac)8(C=C Bu)8], and [Cn2o(hfac)8(CsCCH2Ph)i2] have also been studied. 

Viewed as a whole, it appears that the results of the structural, spectroscopic, theoretical, and other physical studies on metal-alkynyl complexes cannot be interpreted within a single, simple picture of the nature of metal-alkynyl bonding. In view of the fact that understanding the electronic-structural basis of the reactions of metal-alkynyl complexes and the physical properties of the advanced materials developed from them requires a clear picture of this bond, further work in this area would be highly desirable. Of particular value would be studies that applied a combination of the experimental techniques described above and theoretical calculations to a series of archetypal metal-alkynyl complexes from across the transition series, so as both to gauge the effect of the metal on the nature of the M-CCR bond and to clarify the benchmark parameters for each technique within different metal-alkynyl bonding regimes. 

Other work has demonstrated that it is possible to switch ON and OFF luminescence by reduction/oxidation, and it has been demonstrated that such switching is possible inside an OTTLE cell. Many alkynyl complexes, especially those of rhenium, platinum,copper, silver or gold " are highly luminescent from their excited MLCT or metal perturbed 71 states. This opens up the possibility to significantly influence their emissive properties by redox processes. An interesting example is found in recent work of Wong et Unlike other rhenium(I)-alkynyl complexes, heterobimetallic... 

Abstract The NLO properties of iron, ruthenium, osmium, nickel, and gold alkynyl complexes and... 

Powell, C.E., Cifuentes, M.P., McDonagh, A.M., Hurst, S.K., Lucas, N.T., Delfs, C.D., Stranger, R., Humphrey, M.G., Houbrechts, S., Asselberghs, I., Persoons, A., Hockless, D.C.R. OrganometalUc complexes for nonUnear optics. Part 27. Syntheses and optical properties of some iron, ruthenium and osmium alkynyl complexes. Inorg. Chim. Acta 352, 9-18 (2003)... 

Morrall et al. review NLO properties of iron, ruthenium, osmium, nickel, and gold alkynyl complexes, which the authors have prepared. HRS (at 1.064 p,m) and Z-scan (at 0.8 p,m) measurements have been employed. Structure-property relations have been established. Static first hyperpolarizability values have also been computed employing the two-state model. They relate the NLO coefficients to several factors and properties (e.g. ease of oxidation, ir-system length, dimensionality ). 

The NLO properties of cyclopentadienyl metal alkynyl complexes have also proven an especially popular research topic, particularly those containing Group 8 metals. Most of the studies have involved... 

The NLO properties of organometallic and coordination complexes are also rich (21, 184, 279-296). Metal-alkyne complexes were first reported 1960 (297) and have recently attracted significant interest because of their potential in materials applications (2, 298). Studies of these types (299) have resulted in the development of structure-NLO response relationships for quadratic optical nonlinearities (p-value), which increase with valence electron count and ease of oxidation of metal. The amplitude is also tunable by ancillary ligand modification and substitution. Select small alkynyl complexes have been shown to exhibit p values at 1064 nm > 2600 x 10 ° esu (299). 

---