Madelung modified

The neutral-ionic transition (NIT) at t = 0 occurs abruptly[94] when the Madelung energy M of the ionic lattice exceeds the energy I — A to transfer an electron form D to A. Long-range Coulomb interactions are treated self-consistently as part of A in the modified Hubbard model[95],... 

Modified electron-gas procedures also yield quite accurate results for equilibrium and dynamic properties of MgO, if the effect of the Madelung potential upon the oxide ion charge density is properly incorporated, as in the potential-induced breathing model (Mehl et al., 1986, and references therein). As described previously, this approach yields less information than that from a band calculation (e.g., no spectral quantities are obtained), but it is extremely rapid computationally and can readily be extended to low-symmetry situations, so as to evaluate properties such as shear moduli in addition to the bulk moduli readily obtained from the... 

For the Madelung part of the lattice energy, in the case of a salt for which the structure is accurately known, we employed the method of E. F. Bertaut as modified by D. H. Templeton, and evaluated other terms as set out in Ref. 82. When applied to salts that dissociate easily into gaseous molecules, this provided us, via the vant Hofi relationship (see Refs. 80, 82, and 105) with evaluation of the enthalpies of ionization, AH gg [EFa (g) (EFi i)+(g) -I- F (g)] for a variety of F donor molecules, and the fluoride-ion affinities for well known F acceptors, e.g. Ap(BF3) = — AH29g [BF3(g) + F (g) BF4 (g)]. Such evaluations help to provide a more quantitative evaluation of possible reaction chemistry. The intercalation of graphite by one-electron oxidizers and by fluoride-ion acceptors, as covered in Chap. 10, provides examples. Such evaluations are also useful in assessing the likelihood of the existence of salts not yet known, such as [ArFJ fMFg] (see Ref. 92). 

Smith-modified Madelung Indole synthesis (Smith indoie synthesis) ... 

Houlihan, W. J., Parrino, V. A., Uike, Y. Lithiation of N-(2-alkylphenyl)alkanamides and related compounds. A modified Madelung indole synthesis. J. Org. Chem. 1981,46, 4511-4515. 

We now calculate the ground-state energy of an electron gas interacting with the lattice charges through the modified Coulomb potential (131). The calculations follow the same steps as for the case of point charges. We shall therefore merely state the points at which differences must be introduced. This, of course, only happens in the contributions where the lattice plays some role, i.e., the Madelung term and the polarization term. 

NH Deprotonations. During a modified Madelung indole synthesis, the convergent high-yielding condensation of the two main fragments of (—)-penitrem D, Ai-silylation (1.1 equiv BuLi) and lateral metalation (j-BuLi) of a complex o-toluidine substrate followed by condensation with a lactone fragment is carried out (eq 69). ... 

Wacker and Kasireddy described a solid-phase synthesis of 2,3-disubstituted indoles (Scheme 5) [37] via the modified Madelung synthesis reported by Reinhoudt [34, 35]. The basic approach is shown in equation 1, and several synthesized indoles are posted. 

Table 2 Miscellaneous Applications of Modified Madelung Indole Syntheses...

Wadsworth-Emmons process [144], namely, in this case, a modified Madelung-type indole synthesis, into a one-pot transformation. First, reaction between ortho-carbonyl-functionalized aniline 240 and diazocompound 241 in the presence of the Rh(I I)-catalyst generated the phosphonate 243, which, upon treatment with base, was transformed into multisubstituted indoles 242 in moderate to high yields (Scheme 9.86) [145]. 

Recent advances in the synthesis and properties of 4-, 5-, 6-, and 7-azaindoles have been published (13T4767). Rashinkar prepared a series of azaindoles via a modified Madelung indole synthesis. Aminopyridine 261 was treated with acid 262 in the presence of a coupling reagent (BOP-Cl) and base subsequent cyclization furnished azaindole 263 in moderate to good yields (13TL6858). 

The Madelung constant will be written based on its value for NaCl, of Table 4.17, but modified so that to contain the semi-sum of the number of the ions of the gross formula, (1/2) Ep. (a kind of formal average bond, for example equal to 2 for NaCl, or 3 for Ti02). 

The Madelung potential effects were taken into account with Eqs. (6.2) and (6.3). The SCF and modified SCF calculations were carried out at the 6-3IG level, using the in vacuo optimized geometries for the cluster, both in the neutral and ionic forms for the prototype system illustrated by Fig. 3. 

Interactions of an ion M with ions N" at a distance beyond the borders of the WSC will decrease rapidly with increasing interatomic distance in covalent systems. This does not hold for ionic systems, since Coulomb-type interactions fall off slowly. If the ions N" are approximated as point charges with a net charge q, the Madelung potential due to these charges, which can be calculated by the Elwald summation technique as shown in [302], will modify the Fock matrix and the total energy in the following way... 

The approximate electronic-pressure formula, eq. (46), is slightly modified for compounds by inclusion of the Madelung contribution, and becomes... 

Indole 90 was synthesized by a modified Madelung reaction from the amide 89 by treatment with potassium tcrt-butoxide. The presence of two strong electron-withdrawing groups (CN and CF3) in 89 facilitated both the deprotonation to the benzyl anion and its intramolecular cyclization under very mild conditions. Formation of 90 was completed in 10 min at room temperature in 81 % yield [39]. 

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