New donor-acceptor chromophores by formal [2+2] cycloaddition of donor-substituted alkynes to dicyanovinyl derivatives.

The efficient methodology of the cycloaddition between electron-rich alkynes and tetracyanoethylene (TCNE) or 7,7,8,8-tetracyanoquinodimethane (TCNQ), followed by retro-electrocyclisation, is extended to dicyanovinyl derivatives to produce new donor-acceptor push-pull 1,1-dicyanobutadienyl chromophores in excellent to quantitative yield (63-98%) that express strong charge-transfer (CT) absorptions from 300 to 600 nm. The scope of this reaction is established by both varying the nucleophilic and electrophilic components. Electrochemical studies show that the CT properties of these systems are readily tunable by substitution on the electrophile, which has the largest effect on the lowest unoccupied molecular orbital (LUMO).

New strong organic acceptors by cycloaddition of TCNE and TCNQ to donor-substituted cyanoalkynes.

Donor-substituted 1,1,2,4,4-pentacyanobuta-1,3-dienes and a cyclohexa-2,5-diene-1,4-diylidene-expanded derivative were prepared by a [2 + 2] cycloaddition of tetracyanoethene (TCNE) or 7,7,8,8-tetracyanoquinodimethane (TCNQ) to anilino-substituted cyanoalkynes, followed by retro-electrocyclisation; they feature intense bathochromically-shifted intramolecular charge-transfer bands and undergo their first one-electron reductions at potentials similar to those reported for TCNE and TCNQ.

A novel reaction of 7,7,8,8-tetracyanoquinodimethane (TCNQ): charge-transfer chromophores by [2 + 2] cycloaddition with alkynes.

A series of donor-acceptor molecules, featuring intense low-energy intramolecular charge-transfer bands, was prepared by regioselective [2 + 2] cycloaddition between 7,7,8,8-tetracyanoquinodimethane (TCNQ) and N,N-dialkylanilino-substituted (DAA-substituted) alkynes, followed by ring opening of the initially formed cyclobutenes.

Two-dimensional acetylenic scaffolding: extended donor-substituted perethynylated dehydroannulenes.

Starting from (Z)-bis(N,N-diisopropylanilino)-substituted tetraethynylethene (TEE), perethynylated octadehydro[12]- and dodecadehydro[18]annulenes were prepared by oxidative Hay coupling. The dodecadehydro[18]annulene with six peripheral N,N-diisopropylanilino substituents was characterized by X-ray crystallography. Elongation of the Z-bisdeprotected TEE by Cadiot-Chodkiewicz coupling with 1-bromo-2-(triisopropylsilyl)ethyne provided a Z-configured bis(butadiyne), which after alkyne deprotection afforded under Hay coupling conditions N,N-diisopropylanilino-substituted perethynylated hexadecadehydro[20]- and tetracosadehydro[30]annulenes.

Property tuning in charge-transfer chromophores by systematic modulation of the spacer between donor and acceptor.

A series of donor-acceptor chromophores was prepared in which the spacer separating 4-dimethylanilino (DMA) donor and C(CN)(2) acceptor moieties is systematically varied. All of the new push-pull systems, except 4 b, are thermally stable molecules. In series a, the DMA rings are directly attached to the central spacer, whereas in series b additional acetylene moieties are inserted.

Synthesis and characteristics of a nonaggregating tris(tetrathiafulvaleno)dodecadehydro[18]annulene.

A new tris(tetrathiafulvaleno)dodecadehydro[18]annulene with six peripheral n-hexyl substituents was prepared by oxidative Glaser-Hay cyclization of a corresponding diethynylated tetrathiafulvalene (TTF) precursor. The electronic properties of the neutral and oxidized species were studied by both UV/Vis absorption spectroscopy and electrochemistry. From these studies, it transpires that the strongly violet-colored macrocycle does not aggregate in solution to any significant degree, which was confirmed by (1)H NMR spectroscopy.

Donor-substituted 1,1,4,4-tetracyanobutadienes (TCBDS): new chromophores with efficient intramolecular charge-transfer interactions by atom-economic synthesis.

A wide variety of monomeric and oligomeric, donor-substituted 1,1,4,4-tetracyanobutadienes (TCBDs) have been synthesized by [2+2] cycloaddition between tetracyanoethylene (TNCE) and donor-substituted alkynes, followed by electrocyclic ring opening of the initially formed cyclobutenes. Reaction yields are often nearly quantitative but can be affected by the electron-donating power and steric demands of the alkyne substituents. The intramolecular charge-transfer (CT) interactions between the donor and TCBD acceptor moieties were comprehensively investigated by X-ray crystallography, electrochemistry, UV-visible spectroscopy, and theoretical calculations.

Structural and binding features of cofacial bis-porphyrins with calixarene spacers: pac-man porphyrins that can chew.

Based on the efficient combination of calixarene spacers and acetylenic porphyrin derivatives, a new generation of cofacial bis-porphyrins has been synthesized. The first crystal structure of a cofacial bis-porphyrin-calixarene conjugate is reported. Their unique architectural features, analogous to those of pac-man-type bis-porphyrins, allow these calixarene-porphyrin conjugates to adapt their shape to the size of bidentate guests, such as diazabicyclo[2.

Donor-substituted cyanoethynylethenes: pi-conjugation and band-gap tuning in strong charge-transfer chromophores.

An extensive series of silyl-protected cyanoethynylethenes (CEEs) and N,N-dimethylanilino donor-substituted CEEs have been synthesized. More extended chromophores were constructed by selective silyl deprotection and subsequent oxidative acetylenic coupling. The strong electron-accepting nature of the CEEs was revealed by a combination of 13C NMR spectroscopic and electrochemistry measurements.

A new class of organic donor-acceptor molecules with large third-order optical nonlinearities.

Donor-acceptor molecules with 4-(dimethylamino)phenyl donor and 1,1,4,4-tetracyanobuta-1,3-diene acceptor moieties are readily prepared by short, high-yielding routes. The quite small chromophores are characterised by X-ray crystallography and feature intense intramolecular charge-transfer bands, substantial quinoid character in the donor rings, reversible electrochemical reductions and oxidations and powerful third-order optical nonlinearities.

Adjustable cavity for host-guest recognition in cofacial bis-porphyrinic tweezer.

The synthesis of a cofacial bis-porphyrinic tweezer bearing a tris-anthracenic spacer is reported. Its behavior as host has been evidenced as well as the ability of its cavity to adjust to guests of various sizes.

Ground and excited state electronic interactions in a bis(phenanthroline) copper(I) complex sandwiched between two fullerene subunits.

A new fullerene-substituted phenanthroline ligand has been obtained by reaction of a phenanthroline derivative bearing a 1,3-phenylenebis(methylene)-tethered bis-malonate with C(60) in a double Bingel cyclopropanation. The relative position of the two cyclopropane rings in the resulting bis-methanofullerene derivatives has been determined on the basis of the molecular symmetry (C(s)()) deduced from the (1)H and (13)C NMR spectra. The corresponding Cu(I) complex F-Cu-F has been prepared in good yields by treatment of the ligand with Cu(CH(3)CN)(4)BF(4).

A supramolecular cup-and-ball C60-porphyrin conjugate system.

In addition to the ammonium-crown ether recognition, pi-stacking interactions between the C60 sphere and the porphyrin moiety have been evidenced in a supramolecular complex obtained from a porphyrin-crown ether conjugate and a fullerene derivative bearing an ammonium unit.

Bisporphyrins with bischlorin features obtained by direct anodic coupling of porphyrins.

The proximity of two or more porphyrin or chlorin-like structures has been shown to be crucial in numerous biological processes, such as electron transfers. The one-pot electrochemical synthesis of a dimeric tetraphenylporphyrin with one 1,2-(diphenylphosphonium)benzene as a spacer and of its porphyrin-monomer precursor are reported. These new compounds have been characterized by (1)H and (31)P NMR, ESR, and UV-visible spectroscopy and microanalysis.

Donor-substituted cyanoethynylethenes: powerful chromophores for opto-electronic applications.

Donor-substituted cyanoethynylethenes (CEEs) were synthesised, structurally characterised and investigated for their electronic and two-photon absorption properties, revealing exceptionally strong intramolecular charge-transfer interactions.

Molecular engineering of extended chiral and enantiopure multiporphyrinic architectures: Towards the control of their physico-chemical properties.

We report our recent progress in the synthesis and study of extended chiral and enantiopure multiporphyrinic devices. We devoted particular efforts to the study of the influence of both structure and conformation of a molecule on its physicochemical properties, and in this perspective peptides and nucleosides have been chosen as interchromophore linkers. Concerned with the elaboration of molecular wires, we synthesized enantiopure peptides bearing pendant porphyrins.

Donor-substituted peralkynylated "radiaannulenes": novel all-carbon macrocycles with an intense intramolecular charge-transfer.

A novel class of planar, highly conjugated all-carbon macrocycles, which we christened "radiaannulenes", have been prepared based on acetylenic scaffolding using tetraethynylethene (TEE) building blocks; these structures are powerful electron acceptors and, upon peripheral substitution with electron-donating N,N-dialkylanilino groups, display intense intramolecular charge-transfer.

Pi-electron conjugation effects in antiaromatic dehydro[12]- and aromatic dehydro[18]-annulenes.

N,N-Dimethylanilino-substituted perethynylated dehydro[12]- and dehydro[18]-annulenes were prepared by oxidative acetylenic coupling of cis-bisdeprotected tetraethynylethene derivatives obtained by a new photochemical route; they display strongly bathochromically shifted longest-wavelength absorption bands compared to their silyl-substituted counterparts resulting from efficient intramolecular charge-transfer between the peripheral pi-electron donors and the electron-accepting central acetylenic core.

Novel extended tetrathiafulvalenes based on acetylenic spacers: synthesis and electronic properties.

A selection of mono- and diacetylenic dithiafulvalenes was synthesized and employed for the construction of extended tetrathiafulvalenes (TTFs) with hexa-2,4-diyne-1,6-diylidene or deca-2,4,6,8-tetrayne-1,10-diylidene spacers between the two 1,3-dithiole rings. By stepwise acetylenic scaffolding using (E)-1,2-diethynylethene (DEE) building blocks, an extended TTF containing a total of 18 C(sp) and C(sp(2)) atoms in the spacer was prepared. The versatility of the acetylenic dithiafulvene modules was also established by the efficient synthesis of a thiophene-spaced TTF, employing a palladium-catalyzed cross-coupling reaction.

Copper(II/I) Complexes of a Hexakis(bipyridyl)cyclotriveratrylene Ligand: A Redox-Induced Conformational Switch.

A series of copper(II) and copper(I) complexes have been synthesized with ligands combining 6-methyl-2,2'-bipyridines with cyclotriveratrylene (CTV) (1) and with catechol (2). The electrochemical, (1)H NMR, and mass spectrometry characterizations of these complexes are described and discussed. The six pendant bipyridines of ligand 1 allow for the formation of two trinuclear copper(I) complexes [(1)Cu(3)](BF(4))(3) differing only in the conformation "vic" or "int" adopted by the ligand to fit the tetrahedral cuprous ions.

Electrochemical and Spectral Characterization of Iron Corroles in High and Low Oxidation States: First Structural Characterization of an Iron(IV) Tetrapyrrole π Cation Radical.

The electrochemistry and spectroscopic properties of three iron corroles were examined in benzonitrile, dichloromethane, and pyridine containing 0.1 M tetra-n-butylammonium perchlorate or tetra-n-ethylammonium hexafluorophosphate as supporting electrolyte. The investigated compounds are represented as (OEC)Fe(CH), (OEC)FeCl, and (OEC)Fe(py), where OEC is the trianion of 2,3,7,8,12,13,17,18-octaethylcorrole.