Meta-substituted Benzene Research Articles

Synthesis of a Heteroditopic Cryptand Capable of Imposing a Distorted Coordination Geometry onto Cu(II): Crystal Structures of the Cryptand (L), [Cu(L)(CN)](picrate), and [Cu(L)(NCS)](picrate) and Spectroscopic Studies of the Cu(II) Complexes.

The synthesis of a new macrobicyclic cryptand (L) with heteroditopic receptor sites has been achieved in good yields by the [1 + 1] Schiff base condensation of tris(2-aminoethyl)amine (tren) with the tripodal trialdehyde, tris{[2-(3-(oxomethyl)phenyl)oxy]ethyl}amine at 5 degrees C temperature. The crystal structure of L (P2(1)/c, a = 10.756 (5) Å, b = 27.407(9) Å, c = 12.000(2) Å, beta = 116.22(3) degrees, Z = 4, R = 0.060, R(w) = 0.058) shows a pseudo-3-fold symmetry axis passing through the two bridgehead nitrogens. This symmetry is maintained in chloroform solution also, as indicated from its (1)H-NMR spectral data. The cryptand readily forms inclusion complexes with the Cu(II) ion at the tren end of the cavity. The tetracoordinated Cu(II) cryptate (1) thus formed with Cu(picrate)(2) exhibits a very small A(II) value (60 x 10(-)(4) cm(-)(1)) in its EPR spectrum and low-energy ligand field bands in its electronic spectrum in MeCN at room temperature. The bound Cu(II) ion readily accepts the anions CN(-), SCN(-), or N(3)(-), forming distorted trigonal bipyramidal complexes (2-4). The crystal structure of [Cu(L)(CN)](picrate) (2) (P2(1)/C, a = 13.099(1) Å, b = 11.847(8) Å, c = 25.844(7) Å, beta = 91.22(1) degrees, Z = 4, R = 0.056, R(w) = 0.054) has been determined. The equatorial coordination is provided by the three secondary amino N atoms of the tren unit in L, while the two axial positions are occupied by the bridgehead N of the tren unit and the C atom of the cyanide group. One of the equatorial Cu-N bond distances is 2.339(6) Å, which is longer than normal values. The crystal structure of [Cu(L)(NCS)](picrate) (3) (C2/c, a = 47.889(10) Å, b = 10.467(5) Å, c = 16.922(2) Å, beta = 93.90(2) degrees, Z = 8, R = 0.054, R(w) = 0.055) shows the coordination geometry around the Cu(II) ion to be very similar to that in the case of 2. The electronic spectral and EPR spectral data obtained on 2-4 are characteristic of trigonal bipyramidal Cu(II) complexes. The three meta-substituted benzene rings present in L makes the donor atom somewhat rigid in nature which enforces a distorted geometry around the Cu(II) ion.

Studies on Cardiac Ingredients of Plants. VII. Chemical Transformation of Proscillaridin by Means of the Diels-Alder Reaction and Biological Activities of Its Derivatives.

The Diels-Alder reactions of a cardiac glycoside, proscillaridin (1), with some dienophiles were investigated. The reaction of 1 with alkenes such as methyl vinyl ketone and methyl acrylate afforded 3-oxo-2-oxabicyclo[2.2.2]oct-7-enes (2-5) and para-substituted benzene derivatives (6 and 7), while 1 reacted with alkynes (3-butyn-2-one, methyl propiolate) to yield para- or meta-substituted benzene derivatives (6-9). The biological activities of the resulting derivatives were evaluated by the use of isolated guinea-pig papillary muscle preparations and Na+,K(+)-adenosine triphosphatase (ATPase) preparation from dog kidney. Among the proscillaridin derivatives, compounds 4 and 7 moderately inhibited Na+,K(+)-ATPase activity. Furthermore, the concentration range of 7 over which its positive inotropic effect on guinea-pig papillary muscle preparations, increased from 5% to 95% of maximum was broader than that of 1, i.e., concentration dependency was maintained over a greater range of concentration.

Mono- and bi-metallic complexes based on redox-active tris(3,5-dimethylpyrazolyl)borato-molybdenum nitrosyls, part III.(1) Complexes containing meta-substituted benzene- and naphthalenediols or -diamines

The complexes [MoL*(NO)Cl(YC6H4YH-m)] (Y = O or NH), [MoL*(NO)Cl(YC10H6YH-1,5)], (Y = O or NH), [MoL*(NO)Cl(OC10H6OH-2,7)], [{MoL*(NO)Cl}2(XC6H4Y-m)] (X=Y=O, NH or S; X=O, Y=NH), [{MoL*(NO)-C1}2(YC10H6Y-1,5)] (Y=O or NH) and [{MoL*(NO)Cl2-(OC10H6-2,7)] have been prepared and studied by cyclic voltammetry. The monometallic species undergo a reversible oneelectron reduction, whereas the bimetallics undergo two oneelectron reductions. A comparison of ΔE1/2 (E1/2(1)-E1/2(2)) values for those new species with those obtained frompara- substituted analogues and bimetallics containing extended bridges YC6H4ZC6H4Y (e.g. Z = S or CH2CH2) established that the interaction between the redox centres in these new species is intermediate (YC6H4Y-m; NHC10H6NH-1,5) or weak (OC10H6O).

Application of the Seth-Paul-Van Duyse equation—I : A simple relation defining new X +(R) substituent constants on the basis of electrophilic σ + constants

The Seth-Paul-Van Duyse equation (SPVDE) correlating the CO stretching frequencies of a great number of R 1COR 2 molecules with X (R) substituent constants has been reinvestigated. A simple empirical relation defining new X +(R) constants on the basis of electrophilic σ constants has been derived: X + (R) = 0·238 σ + + 1·077. The three earlier reported relationships between the X(R) constants and Hammett σ values have been replaced by this single relationships and a set of new X +(R) constants has been calculated. The new X +(R) constants applied to 287 R 1COR 2 compounds containing the para- or meta-substituted benzene rings fit very well the SPVDE. It has been possible to extend the SPVDE to various aromatic systems.

Formation of linear meta-oligophenyls in the decomposition of polymeric mercury derivatives of meta-substituted benzene compounds by powders of metals

Decomposition of polymer organomercury compounds, obtained from m-diiodo-and m-dibromobenzene and sodium amalgams with powders of palladium or silver, leads to diphenyl and noncyclic m-oligophenyls.

The dimerization and rearrangement of diphenylcyclopropenone: a re-evaluation

The bimolecular reduction of diphenylcyclopropenone yields tetraphenylresorcinol rather than tetraphenylcatechol as previously reported: the reaction involves the rearrangement of a cyclopropene derivative to a meta-substituted benzene.

Studies on the biological activity. II. Discussions on the biological activity of para- and meta-substituted benzene derivatives.

Partition coefficients and biological activities of substituted benzene derivatives have been analysed with respect to the substituent constants σi and σπ, and suggested that they are essentially dependent on the molecular electronic conditions.

Functional-group and substituent effects, both steric and electronic, upon the ultraviolet absorption spectra of some conjugated heteroenoid compounds

The positions of the long-wavelength maxima in the spectra of some 300 compounds of generalized formula I may be accommodated by assuming that the observed maximum is equal to that of styrene + Δλ (the conjugative effect of A) + Δλ′ (the inductive effect of B) + ΣΔλ″ (the sum of the steric effects of the A, B, and phenyl groups) + D (an empirical parameter related to X and Y). These arguments have been extended to the spectra of II. Δλ′ is related to the σ value for meta-substituted benzene derivatives or to σ*. D for meta- and [Formula: see text]para-substituted derivatives roughly correlates with the appropriate σ+ values, whereas D for ortho-substituted derivatives is related to a simple function involving the D value for para substitution and the steric substituent constant, ES. For compounds of generalized formula III, the electronic effects of the A and B groups cancel but the steric effects are additive.Multiple bands occur in the long-wavelength region of the spectra for compounds containing halogen, alkoxy, or amino groups. These groups are highly polarizable and are considered to function both as electron donors and electron sinks.