Molecular associations of [2.2]paracyclophanearylhydrazones with organic acceptors,VIII

Summary Molecular complexes of mono and disubstituted [2.2]paracyclophanehydrazones with organic acceptors have been studied by means of thermodynamic and spectroscopic properties. Furthermore, the enhancement of the donor strength, induced by the hydrazono group, is viewed in the light of substituent as well as transannular effects.

---

Molekulare Assoziation von [2.2]Paracyclophanarylhydrazonen mit organischen Akzeptoren, 8. Mitt.

Zusammenfassung Es wurden Molekülkomplexe von mono- und disubstituierten [2.2]Paracyclophanarylhydrazonen mit organischen Akzeptoren mittels thermodynamischer und spektroskopischer Methoden untersucht. Zusätzlich wird der Anstieg in der Donorstärke, der von der Hydrazonogruppe induziert wird, im Hinblick auf Substituenten- und auch transannulare Effekte diskutiert.

     

Inspheres and inner products

Among normed linear spacesX of dimension ≧3, finite-dimensional Hilbert spaces are characterized by the condition that for each convex bodyC inX and each ballB of maximum radius contained inC,B’s center is a convex combination of points ofB ∩ (boundary ofC). Among reflexive Banach spaces of dimension ≧3, general Hilbert spaces are characterized by a related but weaker condition on inscribed balls. Research of the first author was partially supported by the U.S. National Science Foundation. Research of the second and third authors was supported by the Consiglio Nazionale delle Ricerche and the Ministero della Pubblica Istruzione of Italy, while they were visiting the University of Washington, Seattle, USA.     

Small random perturbations of dynamical systems: Exponential loss of memory of the initial condition

We consider Markov processes arising from small random perturbations of non-chaotic dynamical systems. Under rather general conditions we prove that, with large probability, the distance between two arbitrary paths starting close to a same attractor of the unperturbed system decreases exponentially fast in time. The case of paths starting in different basins of attraction is also considered as well as some applications to the analysis of the invariant measure and to elliptic problems with small parameter in front to the second derivatives. The proof is based on a multiscale analysis of the typical trajectories of the Markov process; this analysis is done using techniques involved in the proof of Anderson localization for disordered quantum systems.     

Complexes of azobisindoles with π-organic acceptors

Complexes of azobisindoles with tetracyanoethylene and tetracyanoquinodimethane were studied by UV-Vis, FT-IR, Raman, NMR and X-ray spectroscopies. FT-IR and Raman spectra, as well as X-ray analysis, gave useful information on the participation of various sites to the association, through analysis of CN and N=N vibrational modes, while UV-Vis and NMR spectra were less helpful. The crystal structure of complexes 1-ethyl-2-phenyl-3-(1-ethyl-2-phenyl-3-azoindole)indole/TCNE,3a and 1,2-diphenyl-3-(1,2-diphenyl-3-azoindole)indole/TCNQ,5b are reported. In the two complexes, the distances between donor and acceptor planes range between 3.4 and 3.5 Å; in3a tetracyanoethylene faces the phenyl ring of the indole, while in5b the superposition of tetracyanoquinodimethane with the donor is negligible. Compound3a,P–1,a=9.504(2),b=9.513(3),c=8.941(2) Å, =97.81(4), =103.38(3), =84.14(2)°,Z=2,D _calc=2.55 g cm^–3; compound5b,P–1,a=12.648(3),b=12.205(2),c=7.263(3) Å, =103.69(2), =91.23(3), =110.61(2)°,Z=2,D _calc=2.53 g cm^–3.     

Reflection geometries over loops

We characterize right loops (L, +) without, respectively with an incidence fibration F from which one can derive a reflection or a point- reflection structure, respectively a reflection or a point- reflection geometry in the sense of [1].     

Metallacycles of porphyrins as building blocks in the construction of higher order assemblies through axial coordination of bridging ligands: solution- and solid-state characterization of molecular sandwiches and molecular wires

Treatment of the octahedral Ru(II)-dimethyl sulfoxide complexes trans-RuCl(2)(dmso-S)(4) (1), trans-RuCl(2)(dmso-O)(2)(CO)(2) (2), and trans-RuCl(2)(dmso)(3)(CO) (3) with a stoichiometric amount of 5,10-bis(4'-pyridyl)-15,20-diphenylporphyrin (4'-cis-DPyP) yields, after chromatographic purification, the novel 2+2 molecular squares of formula [trans,cis,cis-RuCl(2)(dmso-S)(2)(4'-cis-DPyP)](2) (4), [trans,cis,cis-RuCl(2)(CO)(2)(4'-cis-DPyP)](2) (5), and [trans,cis,cis-RuCl(2)(dmso-S)(CO)(4'-cis-DPyP)](2) (6), respectively. Compound 6 exists as an equimolar mixture of the isomeric metallacycles 6a and 6b, depending on whether the 4'-N(py) rings of 4'-cis-DPyP's are trans to CO or to dmso-S. Compounds 4-6 were fully characterized by NMR and IR spectroscopy and by FAB mass spectrometry. Treatment of 5 with excess zinc acetate in chloroform/methanol mixtures led to the isolation of the corresponding zinc adduct [trans,cis,cis-RuCl(2)(CO)(2)(Zn x 4'-cis-DPyP)](2) (5Zn). Treatment of 5Zn with 1 equiv of a trans ditopic N-donor ligand L (L = 4,4'-bipy, 5,15-bis(4'-pyridyl)-2,8,12,18-tetra-n-propyl-3,7,13,17-tetramethylporphyrin (4'-trans-DPyP-npm), or 5,15-bis(4'-pyridyl)-10,20-diphenylporphyrin (4'-trans-DPyP)) leads readily and selectively, according to (1)H NMR spectroscopy, to the quantitative assembling of 2:2 supramolecular adducts of stacked metallacycles of formula [(5Zn)(2)(mu-L)(2)] (7-9), which were thoroughly characterized in solution by NMR spectroscopy. NMR features indicate that, at ambient temperature, the equilibrium between 5Zn and L to yield [(5Zn)(2)(mu-L)(2)] has an intermediate to slow rate on the NMR time scale (relatively broad signals for L) and is totally shifted toward the 2:2 product (all or nothing process). Single-crystal X-ray investigations showed that, depending on the nature of the bridging ligand, in the solid state these sandwich structures can either be maintained or originate polymeric chains formulated as [(5Zn)(mu-L)](infinity). When L = 4'-trans-DPyP, both solution- and solid-state data indicate that [(5Zn)(2)(mu-4'-trans-DPyP)(2)] (9) is a discrete supramolecular assembly of two molecular squares of metalloporphyrins axially connected through other porphyrins. In this molecular box, the two bridging porphyrins are coplanar at a distance of about 11.4 A. When L = 4,4'-bipy, the corresponding adduct 7 has the anticipated sandwich-like discrete architecture [(5Zn)(2)(mu-4,4'-bipy)(2)] in solution, but it assumes a stair-like polymeric wire structure in the solid state. The polymer [(5Zn)(mu-4,4'-bipy)](infinity) is made by 5Zn squares bridged by 4,4'-bipy ligands which are axially coordinated alternatively on the two opposite sides of each square. Our work clearly established that relatively simple supramolecular adducts of porphyrins, such as molecular squares, are suitable building blocks for the construction of more elaborate assemblies of higher order by axial coordination of bridging ligands.     

Strong enhancement of the two-photon absorption of tetrakis(4-sulfonatophenyl)porphyrin diacid in water upon aggregation

A strong enhancement of the two-photon absorption (TPA) cross section of tetrakis(4-sulfonatophenyl)porphyrin diacid (H(4)TPPS(2-)) at various wavelengths when a J-type aggregate is formed in water with respect to the one observed for the H(4)TPPS(2-) monomer in a mixture of water, dimethyl sulfoxide (DMSO), and urea is presented. The TPA properties are characterized by the open aperture Z-scan technique and the ultrafast two-photon absorption spectroscopy with white light continuum probe (TPA-WLCP) technique. The observed enhancement is discussed in terms of possible electronic cooperative effects in the aggregate.     

Enzyme‐Mediated Preparation of Chiral 1,3‐Dioxane Odorants

The enantiomerically enriched diastereoisomers of the chiral 1,3‐dioxane odorants Floropal^® ( 1 ) and Magnolan^® ( 2 ) were prepared by an enzyme‐mediated approach. Their olfactory properties were evaluated to investigate differences in the odor perception for the stereoisomers.     

Divergent sequential reactions of β-(2-aminophenyl)-α,β-ynones with nitrogen nucleophiles

β-(2-Aminophenyl)-α,β-ynones readily react with nitrogen nucleophiles to give three major types of products, depending on reaction conditions and variation in the nucleophiles. The reaction may lead to simple 1,2-nucleophilic adducts or, at higher temperatures, to a divergent sequential cyclisation giving rise to 2-aryl-4-aminoquinolines by reaction with amines, or to substituted 2-aryl or 2-alkyl-4-alkylidene quinazolines by reaction with amidines. The latter could also be synthesised by reaction of β-(2-aminophenyl)-α,β-ynones with iminochlorides.