Ferrocene, optical properties

Again a distorted tetrahedral coordination of Hg is achieved in the l,l-bis(diphenylphos-phino)ferrocene (dppf) complex with Hgl2. Both Hg—P in the dppf chelate ring and terminal Hg—I bonds (averages 256.5 pm and 277.6 pm, respectively) are clearly longer than in the previous examples all angles around Hg are close to the value for a tetrahedron. Nonlinear optical properties of the material have been studied.241... 

Ferrocenes as Materials Displaying Non-linear Optical Properties. One of the most recent applications of ferrocene molecules exploits their non-linear optical properties. Firstly, however, we must describe the concept of ffffnon-linear optical properties.67,68... 

There are many organic and inorganic materials available which exhibit significant non-linear optical properties. In the present context, however, we underline that ferrocene derivatives were the first organo-metallic materials observed possessing non-linear optical properties. In fact, in 1987 it was reported that ci s-ferrocenyl-2-(4-nitrophenyl)ethylene has a 62-fold greater efficiency than urea in generating the second harmonic, Scheme 13.71... 

The electronic and optical properties of such compounds may be expected to respond to external electrical or light stimuli. The NLO properties of a ferrocene containing molecule have been reported (19). 

N=NCeH4, were prepared by reaction of the appropriate amino or anilino ferrocene with [W(NO)Tp Cl2]- Some of these complexes exhibited nonlinear optical properties, in particular, second order harmonic generation, although the response was significantly lower than that of their molybdenum counterparts. 

In other respects, a bis(ferrocenyl)polymethine cation, in which two ferrocene end groups are connected by a polymethine spacer with up to 13 CH units, has been described by Tolbert et al. [14b]. The molecular-wire behavior is claimed, from the optical properties, in particular the absorption energy varying as the reciprocal of the chain length. In addition, separate oxidation potentials were observed for up to 13 carbon atoms between the metal centers. 

Finally, some rather exotic ferrocenes must be mentioned that are formed from chiral helicenes having five-membered terminal rings by deprotonation and reaction with FeCl2-THF complex (Fig. 4-13, bottom) [87, 88]. Such materials have unusual optical properties, e g., extremely high optical rotations. 

Yamamoto, T., et al. 1997. Poly(aryleneethynylene) type polymers containing a ferrocene unit in the pi-conjugated main chain. Preparation, optical properties, redox behavior, and Mbssbauer spectroscopic analysis. Macromolecules 30 5390. 

More recently, a soluble polymer (32) was prepared via reaction of l,l -ferrocenedimethanol with 4,4 -biphenyltetraamine in the presence of [RuCl2(P(C6115)3)3] (70). Approximately 20% of the iron centers were foimd to be in the Fe(III) state as a result of oxidation by ruthenium complexes formed during the polycondensation reaction. Wright and co-workers have reported the synthesis of ferrocene-based polymers possessing nonlinear optical properties (33) (71-73). These polymers were formed by polycondensation of a difunctionabzed ferrocene monomer (71). 

Nishihara, H. Redox and optical properties of conjugated ferrocene oligomers. Bull... 

N. Tsuboya, M. Lamrani, R. Hamasaki, M. Ito, M. Mitsuishi, T. Miyashita, Y. Yamamoto, Nonlinear optical properties of novel carborane-ferrocene conjugated dyads, electron-withdrawing characteristics of car-boranes. J. Mater. Chem. 2002, 12, 2701. 

Sidechain ferrocene-based polymers possessing nonlinear optical properties have been described by Wright and coworkers as shown in Scheme The copolymerization of 5 mol% of the ferrocenyl functionalized monomer 28 with methyl methacrylate 29 resulted in an organometallic polymer (30) displaying second-harmonic-generation activity. The Tg and T values of this organometallic polymer were 120 and 225°C, respectively, which are similar to those of poly(methyl methacrylate). 

Ferrocene polymers with nonlinear optical properties were also prepared via Knoevenagel polycondensation reactions. " Scheme 32 shows the reaction of monomer 123 with 124 to give the accordion polymer 125 with values ranging from 9100 to 26,600." A mixture of A and Z isomers was initially obtained however, an isomerically enriched polymer (98% E isomer) could be isolated through selective precipitation. 

In this paper we will discuss the i thesis and characterization of ferrocene based NLOPs and a study of their orientation and relaxation behavior using NLO-spectroscopy. ° Included in this work is the ( thesis of a new class of fluorenyl-ferrocene NLO-phores and a detailed study of their chemistry and the linear optical properties of the new NLO-phores. The fluorenyl-ferrocene NLO-phore/monomer was successfully incorporated in the backbone of a conjugated organic polymer. 

Not only hemicyanine dyes, but also azo d es have been studied for their nonlinear optical properties. In these compounds the C=C group of the hemicyanine group is replaced by a N=N group (Li et al., 1995,1996 Gao et al., 1995a, 1996b). Another type of complex is the one in which the pyridinium ion is covalently linked to a ferrocene group (Gao et al., 1995b). 

B. Redox, Optical, and Photoisomerization Properties of Azo-Bridged Ferrocene Oligomers... 

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