Cyano bridging

Table 4 Some cyano-bridged binuclear complexes of established structure.

A number of cyano-bridged complexes are included here even though they strictly do not fall in the general family-type defined for the section. The syntheses and photophysical properties of [(NC)(bpy)2Ru(/r-NC)Cr(CN)5] and [(NC)5Cr(Ai-CI Ru(bpy)2(M-NC)Cr(CN)5] have been described. Absorption of visible light by the Ru(bpy)2 unit results in phosphorescence from the Cr(CN)g luminophore, and the results evidence fast intramolecular exchange energy transfer from the MLCT state of the Ru(bpy)2 chromophore to the doublet state of the Cr -based unit. Time-resolved resonance Raman and transient UV-vis absorption spectroscopies have been employed to investigate the MLCT excited states of [(NC)(bpy)2Ru(//-CN)Ru (bpy)2(CN)], [(NC)(bpy)2Ru(//-CN)Ru(phen)2(CN)]+, [(NC)(phen)2Ru(//-CN)Ru (bpy)2(CN)]+, [(NC)(bpy)2... 

Cyano-bridged complexes include both di- and polynuclear systems. Spectroelectrochemical studies of the oxidized and reduced forms of [(bpy)2(CN)Ru(/r-CN)Ru(C (bpy)2] have been carried out. This cation and its reduced form exhibit UV-vis spectra that are consistent with the chromophores being identical. Experimental evidence indicates that the one-electron oxidation... 

The next part of this section focuses on di- and polynuclear Ru"/Os" systems (organized according to the bridging ligands), and pertinent reviews covering multicomponent molecular arrays should be consulted. The cyano-bridged complexes [(bpy)(tpy)Ru(//-CN)Ru" (NH3)5]"+ ( = 3 or 4) have been studied. Picosecond excitation of [(bpy)(tpy)Ru-(//-CN)Ru(NH3)5] results in the observation of a transient intermediate which decays by an... 

Heteroaromatic diols, 40 257 Heterobimetallics, 43 179-254, see also Metals cyano-bridged, 43 244-249 molecular, 43 249... 

D. Modification of Electron Transfer Reactivity upon Cyano-Bridge Formation... 

The Moura group propose the formation of a stable cyano-bridged diiron derivative following ferricyanide oxidation of the superoxide reductases (SORs) from Treponema pallidum and from Desulfovibrio vulgaris.10 Spectroscopic evidence for a ferrocyanide adduct with the bridge (SOR)Fe-NsC-Fen(CN)5 came from mass and IR measurements, where the Fe co-ordination is made up of four equatorial histidine N atoms and an axial cysteinyl S atom, and it is proposed... 

The cyano-bridged trinuclear complex [RuL2(RuL2(CN)2)2] (57) has found to be an excellent photosensitizer for spectral sensitization of the wide-band-gap... 

Many analogues of the dinuclear ammines (Table 47) are known in which ammonia molecules may be considered replaced by ethylenediamine and other bidentate ligands (Table 52). The inter-relations among the complexes are similar to those in Schemes 35 and 36. There are additional examples in the review by Gamer and House302 and other bridged complexes are covered in Sections 35.4.1.1, 35.4.2.3.vi, 35.4.2.4, 35.4.2.5, 35.4.4.2, 35.4.4.10, 35.4.7.4 and 35.4.8.3. Cyano-bridged complexes are listed in Table 45. 

A number of cyano-bridged coordination polymers with Prussian Blue-related structures, in which extended linear Ag(CN)2 or AufCNH bridges take the place of the OT bridges of the prototype, show 3-fold interpenetration [1]. A typical example is that of Rb[Cd Ag(CN)2)3] consisting of Rb+ cations and a 3-fold interpenetrating polymeric anion, whose structure is shown in Figure 31. 

Figure 38. Self-penetrating, self-catenating structure of Cd(CN)2- pyrazine. Circles represent Cd. Short connections between Cd atoms represent cyano bridges within the (4,4) Cd(CN)2 sheets and longer connections represent the pyrazines linking sheet to sheet Two catenated 6-gons are highlighted.

Figure 39. Structure of Cd(CN)2-4,4 -bipy. Circles represent Cd. Heavy connections represent cyano bridges and open connections represent bipys.

Such conclusions are, however, extremely speculative at present. The Fe(CN) 3"/ system suffers from a number of complications, including the possibility of surface reactions to form Prussian Blue-like cyano-bridged chains. Details of these results will be given in a forthcoming publication. (14) This brief summary is included here in order to illustrate how information on electron delocalization effects for adsorbed redox couples might be obtained, at least in principle, by examining potential-dependent SERS frequencies. 

Reactions similar to reaction 5 have resulted in numerous cyano-bridged cluster-containing solids, and these are enumerated in Table V. While all but a... 

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