A-Diimine complexes

In a series of studies of the spectroscopy and photochemistry of nickel(O) -a-diimine complexes, the structural differences among the complexes NiL2 and Ni(CO)2L (L Q-diimine) have been examined by means of molecular orbital calculations and electronic absorption Raman resonance studies.2471, 472 Summing up earlier work, the noninnocence of a-diimine ligands with a flat — N=C—C=N— skeleton in low-valent Ni chemistry and the course of substitution reactions of Ni° complexes with 1,4-diaza-1,3-dienes or a,a -bipyridine have been reviewed.2473... 

Bulk NLO studies on luminescent /uc- ReI(CO)3(a-diimine) + complexes by Yam and co-workers note SHG from surfactant derivatives such as (54) and (55) deposited in Langmuir-Blodgett (LB) thin films.110-112 For example, the 532 nm SHG from LB films of the stilbazole derivative (55) is ca. 50% more intense than that from films of the structurally related purely organic salt traiw-.lV-methyl-4-[2-(4-octadecyloxyphenyl)ethenyl]pyridinium iodide.112... 

The cubic NLO properties of Ru11 tris-(a-diimine) complexes have been investigated only relatively recently by Ji and co-workers using 540 nm Z-scan all of the complexes studied exhibit both NLO absorption and SDF behavior.135-138 The large and 7 values of complexes such as (73) depend on the position of the -N02 group in the order 4- > 2- > 3-.135 Also, the NLO responses decrease on deprotonation of the imidazolyl nitrogens (although this effect is only... 

RR excitation profiles from a series of M(CO)4(a,a -diimine) complexes have identified additional y-polarized (dx2-z2) ai - b2 (n ) and x-polarized (dxy) a2 -> b2 (n ) MLCT transitions in the absorption band envelope, although the latter component is relatively weak for substituted phen derivatives [63], These absorption features are observable in the 80 K spectrum of W(CO)4(4-Me-phen) in EPA (see Fig. 2). The most intense MLCT components in the low-temperature spectrum appear at 444 and 468 nm, and these are associated with the ai -> b i and b2 -> b i transitions, respectively [60],... 

The dual luminescence bands exhibited by the M(CO)4(a,a/-diimine) complexes in room-temperature solution are unusual and have been further explored by excitation wavelength studies [60], The higher energy emission band is seen to increase substantially in intensity as shorter exciting wavelengths are used... 

Keywords TDDFT Excitation energies Excited states Transition metal complexes Electronic spectra Metallotetrapyrroles Metallocarbonyls a-diimine complexes Porphyrins Porphyrazines Phthalocyanines Werner complexes Sandwich complexes... 

It is convenient to note here that the oxidative dehydrogenation of diamines such as ethylenediamine and cage type amines136 can lead to a-diimine complexes. 

Metal-to-Ligand-Charge-Transfer (MLCT) States in M(H)(CO) (a-diimine) Complexes (M = Mn, Re)... 

Pt(NH3)6]" + reacts with acacH to give (6) in which a diimine complex has been formed by loss of water. The Pfr amido complex K2[Pt(NH2)6] is also known. ... 

It is now recognized that in particular for the case of iron(II), even a-diimine complexes give spectra similar to the Fe(II)(bipy) + cation. Also systems with the grouping —Fe(II) N=C—C=N—C—C—N—... 

The effects of variation of the donor substituents and the metal centre have also been investigated in 1320 nm HRS studies with compounds related to 28 and 29 by Le Bozec and colleagues [71, 73], Even though the relatively complicated electronic structures of such tris-(a-diimine) complexes hinders the development of deal structure-activity relationships, the smaller of 30 (298 x 10 ° esu in chloroform) clearly corresponds with a higher ILCT energy when compared with... 

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