Macrocyclic donors

The 14-membered macrocycle 1,4,8,11-tetraazacyclotetradecane (cyclam or [14]aneN4), unlike cyclen, is capable of encircling most transition metal ions and in the case of Co111 the trans configuration is much preferred by comparison with the folded cis isomer. Electrochemical reduction of A,v-[Co(cyclam)(OI I)2]+ in 3M NaOH leads to rapid isomerization to the trans form, and the relative stabilities of the trans and cis isomers of the di- and trivalent complexes were determined from a thermodynamic cycle.702 This preference for trans orientation of the non-macrocyclic donors has enabled the isolation and investigation of many Co complexes without the complications of isomerization. Some novel examples include /r[Pg.61]

Ru(II) Complexes with Porphyrin, Phthalocyanine and Macrocyclic Donors... 

In the case of cationic complexes with unsaturated macrocycles two molecules of nucleophile, such as ammonia, amines and alkoxides, add to carbon atoms of two inline groups. For example, the reaction of [Ni(Bzo[16]octaeneN4)](C104)2 (Table 106) with sodium methoxide or ethoxide yields the compounds (395),2860 while with secondary amines and diamines complexes of type (396) are obtained.28 1 The reaction of (396) with acetone at room temperature yields complex (397) where the enolate anion of acetone, MeC(0)CH2, replaces the diethylamide group (Scheme 58). 2862 The addition of molecules such as bis(2-hydroxyethyl)methylamine and bis(2-hydroxyethyl) sulfide, HOCH2CH2YCH2CH2OH (Y = NMe, S) results in the formation of derivatives which possess one more coordination site just above the plane of the macrocyclic donors (398).2863... 

One of the rare examples of Cu(I) and Cu(II) complexes with identical donor sets and closely related geometries is illustrated in Fig. 13 (68, 69). At first sight the structures appear veiy similar in each case the copper atom is coordinated to all five macrocyclic donors and the geometry lies somewhere between trigonal bipyramidal and square pyramidal. On closer inspection, however, some differences become apparent. In [Cu(L13)](CI04) the Cu(I) ion bonds most strongly to N9, S2, and S16, and the bonds to the imine nitrogen atoms are relatively... 

The substitution of 3,6-dioxaoctane-l,8-diamine for 3,6-diazaoctane-1,8-diamine in a template synthesis with 2,6-diacetylpyridine on iron(II) yields the mixed donor macrocycle (127). This molecule also forms a seven-coordinate iron(II) complex [Fe(L)(NCS)2] (L = 127). This blue high-spin complex (room temperature magnetic moment = 5.44 BM) exhibits an electronic spectrum and electrochemical behaviour which indicate that the complex of the mixed donor oxygen-containing macrocycle stablizes the -I- 2 oxidation state to a greater extent than the same complex of the corresponding macrocyclic pentamine. The seven-coordinate high-spin iron(TT) complex [Fe(L)(H,0),] (L = 128) of the related macrocycle (128) is formed by the condensation of 2,9-di-(l-methylhydrazino)-l,10-phenanthroline with 2,6-diacetylpyridine in the presence of fresh FeClj HjO. The X-ray crystal structure of this complex clearly shows that the iron(II) atom is coplanar with the macrocyclic donor set. 

Fig. 6.16 Potassium cation sensor as a molecular fluorescence switch in a PET process of anthracene fluorophore having a macrocyclic donor unit...

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