1,1-Dicyano-4-[4-(diethylamino)phenyl]buta-1,3-dienes: Structure–Property Relationships

We report the synthesis and physical study of a series of 1,1- dicyano-4-[4-(diethylamino)phenyl]buta-1,3-dienes in which the number and position of additional CN substituents along the 1,1-dicyanobuta-1,3-dienyl fragment is systematically varied. While X-ray analysis provided unambiguous infor- mation about molecular geometries in the crystal, UV/Vis and electrochemical measurements, by cyclic voltammetry (CV) and rotating disk voltammetry (RDV), revealed that in- troduction of additional cyano groups in the C2- and C4-posi- tions most affected the optical properties of these molecules in solution, in terms of intramolecular charge-transfer ab- Introduction π-Conjugated donor–acceptor (D–A) chromophores have been investigated for quite some time,[1,2] but have re- cently attracted renewed interests for potential applications in the fabrication of opto-electronic materials.[2–4] The en- ergy and intensity of their characteristic intramolecular charge-transfer (ICT) transitions depend on the strength of the electron donor and acceptor moieties and the nature of the π-conjugated spacer.[5–8] While the nature of the donor, acceptor, and π-conjugated spacer have been systematically varied,[9] the number and positioning of the push/pull sub- stituents along the π-conjugated spacer backbone has only been addressed in a few cases.[10] Our group has observed strong electro-optical effects associated with the increasing number of cyano groups in push–pull chromophores;[10e,11] [a] Laboratorium für Organische Chemie, ETH Zürich, Hönggerberg, HCI, 8093 Zürich, Switzerland Fax: +41-44-632-1109 E-mail: [email protected] [b] Laboratoire d’Electrochimie et de Chimie Physique du Corps Solide UMR 7177, CNRS, Université de Strasbourg, 4, rue Blaise Pascal, CS 90032, 67081 Strasbourg Cedex, France [c] Advanced Technology Institute and Department of Physics, University of Surrey, Stag Hill, Guildford GU2 7XH, Surrey, United Kingdom [d] Department of Physics and Center for Optical Technologies, Lehigh University, 415 Lewis Lab, 16 Memorial Dr. East, Bethlehem, PA 18015, USA Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/ejoc.201200111. sorption energy and intensity. A comparison with structurally related chromophores indicates that the shift of the anilino donor from position 2/3 to 4 along the butadiene scaffold re- sults in a remarkable bathochromic shift of the ICT absorp- tion maxima, mainly due to the higher planarity in the pres- ent series. These findings are further corroborated by density functional theory calculations. Preliminary nonlinear optical (NLO) measurements confirm the promise of the new push- pull chromophores as third-order nonlinear-optical molecular materials

1,1-Dicyano-4-[4-(diethylamino)phenyl]buta-1,3-dienes: Structure–Property Relationships

We report the synthesis and physical study of a series of 1,1- dicyano-4-[4-(diethylamino)phenyl]buta-1,3-dienes in which the number and position of additional CN substituents along the 1,1-dicyanobuta-1,3-dienyl fragment is systematically varied. While X-ray analysis provided unambiguous infor- mation about molecular geometries in the crystal, UV/Vis and electrochemical measurements, by cyclic voltammetry (CV) and rotating disk voltammetry (RDV), revealed that in- troduction of additional cyano groups in the C2- and C4-posi- tions most affected the optical properties of these molecules in solution, in terms of intramolecular charge-transfer ab- Introduction π-Conjugated donor–acceptor (D–A) chromophores have been investigated for quite some time,[1,2] but have re- cently attracted renewed interests for potential applications in the fabrication of opto-electronic materials.[2–4] The en- ergy and intensity of their characteristic intramolecular charge-transfer (ICT) transitions depend on the strength of the electron donor and acceptor moieties and the nature of the π-conjugated spacer.[5–8] While the nature of the donor, acceptor, and π-conjugated spacer have been systematically varied,[9] the number and positioning of the push/pull sub- stituents along the π-conjugated spacer backbone has only been addressed in a few cases.[10] Our group has observed strong electro-optical effects associated with the increasing number of cyano groups in push–pull chromophores;[10e,11] [a] Laboratorium für Organische Chemie, ETH Zürich, Hönggerberg, HCI, 8093 Zürich, Switzerland Fax: +41-44-632-1109 E-mail: [email protected] [b] Laboratoire d’Electrochimie et de Chimie Physique du Corps Solide UMR 7177, CNRS, Université de Strasbourg, 4, rue Blaise Pascal, CS 90032, 67081 Strasbourg Cedex, France [c] Advanced Technology Institute and Department of Physics, University of Surrey, Stag Hill, Guildford GU2 7XH, Surrey, United Kingdom [d] Department of Physics and Center for Optical Technologies, Lehigh University, 415 Lewis Lab, 16 Memorial Dr. East, Bethlehem, PA 18015, USA Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/ejoc.201200111. sorption energy and intensity. A comparison with structurally related chromophores indicates that the shift of the anilino donor from position 2/3 to 4 along the butadiene scaffold re- sults in a remarkable bathochromic shift of the ICT absorp- tion maxima, mainly due to the higher planarity in the pres- ent series. These findings are further corroborated by density functional theory calculations. Preliminary nonlinear optical (NLO) measurements confirm the promise of the new push- pull chromophores as third-order nonlinear-optical molecular materials

Comparison of CC triple and double bonds as spacers in push-pull chromophores

We report the synthesis and properties of two series of homologous donor–acceptor (D–A) chromophores in which N,N-dimethylanilino (DMA) or N,N-dihexylanilino (DHA) donors and dicyanovinyl acceptors are separated by up to four C≡C triple-bond spacers or up to three C=C double-bond spacers. The intramolecular charge-transfer (CT) interactions of the new D–A oligoynes and the known all-trans D–A oligoenes were investigated by X-ray crystallography, electrochemistry, UV/Vis spectroscopy, and theoretical calculations. In both series, the optical and electrochemical HOMO–LUMO gaps decrease with increasing spacer length. The HOMO–LUMO gaps for the D–A oligoynes and oligoenes with a given spacer length are nearly identical. The effect of the spacer length was found to level-off for spacers with more than six carbon atoms. The third-order optical nonlinearity of both series of molecules was determined by measuring the rotational averages of the third-order polarizabilities rot by degenerate four-wave mixing

Comparison of CC triple and double bonds as spacers in push-pull chromophores

We report the synthesis and properties of two series of homologous donor–acceptor (D–A) chromophores in which N,N-dimethylanilino (DMA) or N,N-dihexylanilino (DHA) donors and dicyanovinyl acceptors are separated by up to four C≡C triple-bond spacers or up to three C=C double-bond spacers. The intramolecular charge-transfer (CT) interactions of the new D–A oligoynes and the known all-trans D–A oligoenes were investigated by X-ray crystallography, electrochemistry, UV/Vis spectroscopy, and theoretical calculations. In both series, the optical and electrochemical HOMO–LUMO gaps decrease with increasing spacer length. The HOMO–LUMO gaps for the D–A oligoynes and oligoenes with a given spacer length are nearly identical. The effect of the spacer length was found to level-off for spacers with more than six carbon atoms. The third-order optical nonlinearity of both series of molecules was determined by measuring the rotational averages of the third-order polarizabilities rot by degenerate four-wave mixing

Development of Functionalized Cyclotriveratrylene Analogues: Introduction of Withdrawing and π-Conjugated Groups

International audienceCyclotriveratrylene analogues (CTVs) are supramolecular bowl-shaped molecules known for their ability to complex organic and organometallic guests, to form liquid crystals, polymers, or nanostructures. In this Article, we report the synthesis of new cyclotriveratrylene analogues with fluorescence properties in which various electron-withdrawing or π-extended conjugated groups are appended to the wide rim ortho to the methoxy-donating groups. Synthetically, these functionalized CTVs cannot be obtained as CTVs with electron-rich functions by the typical method (i.e., the trimerization of the corresponding benzyl alcohol) but are prepared from a common key intermediate, the C3-triiodocyclotriveratrylene (CTV-I3), in good yields. Despite the synthetic difficulties encountered due to the presence of three reactive centers, we have demonstrated the possibility of performing Sonogashira coupling and Huisgen cycloaddition reactions directly to the CTV core for the first time. CTVs with π-extended conjugated groups reveal interesting fluorescence profiles. More broadly, this study utilizes CTV-I3 to introduce novel functionalities into CTVs to keep exploring their potential applications. Cyclotriveratrylene analogues (CTVs) are supramolecular bowl-shaped molecules known for their ability to complex organic and organometallic guests, to form liquid crystals, polymers, or nanostructures. In this Article, we report the synthesis of new cyclotriveratrylene analogues with fluorescence properties in which various electron-withdrawing or π-extended conjugated groups are appended to the wide rim ortho to the methoxy-donating groups. Synthetically, these functionalized CTVs cannot be obtained as CTVs with electron-rich functions by the typical method (i.e., the trimerization of the corresponding benzyl alcohol) but are prepared from a common key intermediate, the C3-triiodocyclotriveratrylene (CTV-I3), in good yields. Despite the synthetic difficulties encountered due to the presence of three reactive centers, we have demonstrated the possibility of performing Sonogashira coupling and Huisgen cycloaddition reactions directly to the CTV core for the first time. CTVs with π-extended conjugated groups reveal interesting fluorescence profiles. More broadly, this study utilizes CTV-I3 to introduce novel functionalities into CTVs to keep exploring their potential applications