Complex ionic donor-acceptor

Conduction in strong (ionic) donor-acceptor (charge-transfer) complexes and radical-ion... 

CONDUCTION IN STRONG (IONIC) DONOR-ACCEPTOR (CHARGE-TRANSFER) COMPLEXES AND RADICAL IONS SALTS... 

Figure 3.36 Phase diagram of ionic donor-acceptor complexes of polymer (17a) and monomer (20) (dBrSzNO ) with n = 6 and Br (permission being sought from [74]).

Concerning my research during my Dow years, as I discuss iu Chapter 4, my search for cationic carbon intermediates started back in Hungary, while 1 was studying Friedel-Crafts-type reactions with acyl and subsequently alkyl fluorides catalyzed by boron trifluoride. In the course of these studies I observed (and, in some cases, isolated) intermediate complexes of either donor-acceptor or ionic nature. 

The strength of the complexation is a function of both the donor atom and the metal ion. The solvent medium is also an important factor because solvent molecules that are potential electron donors can compete for the Lewis acid. Qualitative predictions about the strength of donor-acceptor complexation can be made on the basis of the hard-soft-acid-base concept (see Section 1.2.3). The better matched the donor and acceptor, the stronger is the complexation. Scheme 4.3 gives an ordering of hardness and softness for some neutral and ionic Lewis acids and bases. 

Let us now examine the consequences of the formation of a donor-acceptor bond in a little more detail. If the donor - acceptor bond is completely covalent, then we record net transfer of one unit of charge from the donor to the acceptor as a direct consequence of the equal sharing of the electron pair between the two centres. This result leaves a positive charge on the donor atom and a negative charge on the acceptor atom. The limiting ionic and covalent descriptions of a complex cation such as [Fe(H20)6] are shown in Fig. 1-1. 

Likewise, cationic acceptors afford mixed (positively) charged complexes with electron-rich donors,11 i.e., [D, A+] and anionic donors associate with electron-poor acceptors to form mixed (negatively) charged complexes,12 i.e., [D-, A]. In each case, the intermolecular (ionic) complexation or association represents the highly oriented organization of the donor/acceptor pair (independently of whether they bear positive, negative or no charge) that is often sufficient to afford crystalline complexes amenable to direct X-ray structure elucidation.13... 

Problem Use the data in Tables 5.7 and 5.8 and Figs. 5.5 and 5.7 to estimate the relative importance of donor-acceptor interactions in neutral versus ionic H-bond complexes. 

Solution If we compare the ratio of estimated donor-acceptor interaction (A Ena52>) with the full H-bond energy (A fun) for ionic HO HA versus neutral H20- HA complexes, we And the following values ... 

Some semiconducting organic CT complexes of mixed-stack architecture exhibit the rather unusual neutral-to-ionic (N-I) phase transition upon variation of an external variable of parameter hyperspace, such as P or r. The transition manifests itself by a change of q and a dimerization distortion with the formation of donor-acceptor dimers along the stacking axis in the I-phase. 

Figure 1. Distinct approaches to the template synthesis of molecules with mechanical bonds ionic coordination complex I, ionic electron donor-acceptor complex II and neutral complex III with hydrogen bonds.

Fig. 22 Electronic structures of some solid molecular complexes O, non-ionic complexes , ionic complexes. The complexes are arranged by the difference between the ionization potential of the donor and the electron affinity of the acceptor. (After Matsunaga, 1975)...

The lanthanide phthalocyanine complexes, obtained by conventional methods starting from metal salts at 170-290°C and phthalonitrile (Example 26), contain one or two macrocycles for each metal atom [5,6,8,63,82,84-98]. Thus, according to Refs. 6,63, and 85, the complexes having compositions LnPc2H, XLnPc (X- is halide anion), and Ln2Pc3 (a super-complex ) were prepared from phthalonitrile as a precursor the ratio of the reaction products depends on the synthesis conditions and the metal nature. The ionic structure Nd(Pc)+Nd(Pc)2 was suggested [85] and refuted [63] for the neodymium super-complex Nd2Pc3 the covalent character of the donor-acceptor bonds in this compound and other lanthanide triple-decker phthalocyanines was proved by the study of dissociation conditions of these compounds [63]. 

Dyes are relatively complex organic structures inducing different concomitant interactions. They contains most of the time sulfonate groups with a strong ionic effect they are constituted of multiaromatic rings with donor-acceptor effect described as major contribution in chromatography hydrophobic interactions are also promoted by their chemical structure. 

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