Sandwich complexes optical properties

Optical Properties. The double-decker complexes of porphyrazines have characteristic electronic absorption spectra (Table V). The intense Soret bands of the double-decker complexes are blue shifted with respect to the single pz ligand as a consequence of the strong n-n interactions. Another characteristic of sandwich compounds is the additional appearance of absorption bands shifted to the red (termed Q ) and to the blue (termed Q") of the normal g-band region. These new transitions are thought to result from orbitals delocalized over the two macrocyclic ligands (33, 82). 

The synthesis of new materials having novel electronic or optical properties is of great current interest. One approach to the synthesis of such materials is to systematically link small sandwich units together to form an extended multi-decker sandwich system. Immediately following the discovery of the triple-decker structure of the Cp3Ni2+ complex in early 1970s,181 Grimes and co-workers synthesized the first neutral triple-decker metallacarborane sandwich compound. Most of the subsequent research in this field, some of which has been described... 

TDDFT methods have also been applied successfully to the description of the linear and nonlinear optical properties of heteroleptic sandwich complexes. The optical spectrum and the hyperpolarizability of Zr(OEP)(OEPz,) for which large first hyperpolarizabilities, /JSHG (SHG=second-harmonic generation) were measured in an electric field induced second-harmonic generation (EFISH) experiment [182], have been investigated by TDDFT methods [134]. The excitation energies and oscillator strengths calculated... 

Among phthalocyanine (Pc) derivatives, the syntheses of lanthanide (III) Pcs (LnPc2) have attracted great attention due to the changing of the electrochemical responses of the complexes with the n-n interaction of the Pc rings of the sandwich complexes [76-80]. Altering the metal center and substituents of these type complexes easily affects their physical, electrical, optical, and electrochemical properties [81-83], thus it is important to determine the electrochemical responses of the newly synthesized complexes to decide their possible application in different... 

Ricciardi, G., Rosa, A., van Gisbergen, S. J. A., 8c Baerends, E. J. (2000). A density functional study of the optical spectra and nonlinear optical properties of heteroleptic tetrapyr-role sandwich complexes the porphyrinato-porphyrazinato-zirconium(IV) complex as a case study. Journal of Physical Chemistry A, 104, 635-643. 

Compositions of HTSC and ultrathin layers of dyes also exhibit interesting properties [434]. The potentiality of electrosynthesis for fabrication of such structures with specific optical transitions is excellent, particularly as a result of experience gained in studies and applications of the electrochromism phenomenon [435] such as forming films of poorly soluble cyanide complexes [436-441]. These compounds provide the opportunity to carry out electrochemical fabrication of linked and sandwich structures. The region of potential during deposition corresponds to the stability regions of HTSC surfaces. 

Since simple ketones typically coordinate more weakly to metals than olefins, many Rh-phosphane complexes may show poor activity for the hydrogenation of simple ketones. However, the catalytic properties of cyclometalated half-sandwich Rh(lII) complexes 99-101, isolated or prepared in situ firom metal precursors and optically pure secondary amines, were evaluated, among which the complex 100 showed the highest productivity in the reduction of acetophenone with a i-PrOH/t-BuOK reductant system (Fig. 26) [93]. The complex 99 afforded good yield of alcohol products from acetophenone, but the enantioselectivity was low, while the cyclometalated imine 101 was almost inactive. The rhodacycle 100, which was formed in situ, efficientiy catalysed the reduction of substrates 102 (92 % ee), 103 (93 % ee) and 104 (91 % ee), with substrate 103 showing total chemoselectivity. For substrates 105,106 and 107, however, lower ee values were observed (<85 %). 

The non-linear optical (NLO) properties of organometallic complexes have attracted significant attention over the past In this context, a series of half-sandwich alkynyl and enynyl ruthenium(ll) and osmiun(n)... 

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