Non-planar push–pull chromophores

Abstract

The development of a unique class of non-planar push-pull chromophores by means of [2 + 2] cycloaddition, followed by cycloreversion, of electron-deficient olefins, such as tetracyanoethene (TCNE), 7,7,8,8-tetracyanoquinodimethane (TCNQ) and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F(4)-TCNQ), as well as dicyanovinyl (DCV) and tricyanovinyl (TCV) derivatives, to donor-substituted alkynes is explored in this feature article. This high-yielding, "click-chemistry"-type transformation with acetylenic dendrimers affords dendritic electron sinks capable of multiple electron uptake within a narrow potential range. An [AB]-type oligomer with a dendralene backbone was synthesised by a one-pot, multi-component cascade reaction of polyyne oligomers with TCNE and tetrathiafulvalene (TTF). In most cases, the resulting chromophores feature intense intramolecular charge-transfer bands extending far into the near infrared region and some of them display high third-order optical nonlinearities. Despite substitution with strong donors, the electron-withdrawing moieties in the new chromophores remain potent acceptors and a number of them display positive first reduction potentials (vs. the ferrocenium/ferrocene (Fc(+)/Fc) couple in CH(2)Cl(2)), which rival those of parent TCNE, TCNQ and F(4)-TCNQ. The non-planarity of the chromophores strongly enhances their physical properties when compared to planar push-pull analogues. They feature high solubility, thermal stability and sublimability, which enables formation of amorphous, high-optical-quality thin films by vapour phase deposition and makes them interesting as advanced functional materials for novel opto-electronic devices.

Postfunctionalization of aromatic polyamine by [2+2] cycloaddition of 7,7,8,8-tetracyanoquinodimethane with side chain alkynes

“…The precursor polyamine P1 revealed no relationship between the absorption spectra and solvent polarity. However, similar to some small molecules and polymers containing this class of donor-acceptor chromophores [39,40], P2 (x ? y = 1) displayed a clear positive solvatochromism.…”

Visualizing the Product of a Formal Cycloaddition of 7,7,8,8‐Tetracyano‐p‐quinodimethane (TCNQ) to an Acetylene‐Appended Porphyrin by Scanning Tunneling Microscopy on Au(111)

“…Herein, we describe a click-type on-surface reaction, with the reaction product as obtained in a formal [2 + 2] cycloaddition, followed by retro-electrocyclization between electron-deficient 7,7,8,8-tetracyano-p-quinodimethane (TCNQ) and acetylene-appended porphyrin 1 (Scheme 1). [9] By means of ultrahigh vacuum (UHV) STM, we were able to identify single molecules both before and after the transformation.…”

Facile synthesis of functional poly(vinylene sulfide)s containing donor–acceptor chromophores by a double click reaction

“…21,22 In the structures of poly(vinylene sulfide)s, the delocalization of π-electrons through the sulfur bridge may endow the polymers with an array of remarkable characteristics, such as light refractivity, nonlinear optical property and so on. [23][24][25][26][27][28][29] The reactions are with significant advantages that the products feature strong charge-transfer (CT) interactions in the visible absorption region, potent redox activities, and are useful for optimization of the electronic states, thereby leading to the enhanced performance of the optoelectronic devices, such as photovoltaic cells. [23][24][25][26][27][28][29] The reactions are with significant advantages that the products feature strong charge-transfer (CT) interactions in the visible absorption region, potent redox activities, and are useful for optimization of the electronic states, thereby leading to the enhanced performance of the optoelectronic devices, such as photovoltaic cells.…”