Designing of Push–Pull Chromophores with Tunable Electronic and Luminescent Properties Using Urea as the Electron Donor

Abstract

Urea-functionalized 4-ethynylbenzenes undergo facile formal [2 + 2] cycloaddition followed by retroelectrocyclization upon reaction with tetracyanoethylene, yielding 1,1,4,4-tetracyanobuta-1,3-dienes-based push–pull chromophores. Unlike the N,N′-dialkylamino group, urea functionalization provides easy access to further functionalization on these chromophores. The resulting chromophores exhibit unexpected white light emissions apart from various inherent properties like intramolecular charge-transfer band and redox behavior.

A subtle change in substituent enabled multi-ways fluorine anion signals including paper-strip colorimetric detection using urea-functionalized push–pull chromophore receptor

“…[18] Recently, we demonstrated a methodology for the synthesis of mono (C2)-substituted 1,1,4,4tetracyano-1,3-butadienes (TCBDs) including compound mono-TCBD with urea moiety as EDG, which exhibited unusual luminescence property with white-light emission (Figure 1). [19] However, its use in sensing of Fion in combination with urea moiety has not been reported before. Molecular structure of mono-substituted TCBD.…”

“…Molecular structure of mono-substituted TCBD. [19] Hence, upon testing they failed to exhibit Fsensing ability based on UV/Vis, fluorescence, and more importantly naked-eye detection in both solution as well as in solid-phase (Figure S16, Supporting Information). Failure to sense Fcan be attributed to the aggregation phenomenon between intermolecular urea moieties leading to unavailability H-donors for fluoride.…”

“…Failure to sense Fcan be attributed to the aggregation phenomenon between intermolecular urea moieties leading to unavailability H-donors for fluoride. [19,20] We envisaged that substitution of mono-TCBD at the C3-position with phenyl (Ph) and 4-(dimethylamino)phenyl (DMA) would retain the single molecular integrity of resulting 2,3-disubstituted 1,1,4,4tetracyanobuta-1,3-dienes 1 and 2, respectively due to the absence of relatively unstable free dicyanovinyl (DCV) moiety (Figure 1, Scheme 1). [19] Herein, we show that how the judicious choice of substituents at the C3-position in non-planar push-pull chromophores 1 and 2 led to multi-ways Fdetection including non-chemical treated paper-strip based colorimetric sensing under aqueous medium.…”

Synthesis of 1,1,4,4‐Tetracyanobuta‐1,3‐Dienes using Tetracyanoethylene Oxide via [3+2]‐Cycloaddition‐Ring Opening Reaction

“…In general, the previous works reported on the synthesis of TCBDs based push‐pull chromophores have mostly altered the donor moiety on the alkyne part, such as metal ylides, [16] thiophenes, [17] amines, [11] ferrocene and TTF, [18] azulene, [19] porphyrin, [20] carbazole, [21] ynamide, [22] and recently urea [23] . Whereas, in the case of the acceptor part, CN derivatives especially tetracyanoethene (TCNE) has been predominantly used as benchmark starting material [11c] .…”

Synthesis, Characterization and Unusual Near-Infrared Luminescence of 1,1,4,4-Tetracyanobutadienes

“…17 Furthermore, some investigations have emerged that circumvent the discussed pitfalls: the aggregation-induced emission from J-aggregates of a bis-TCBD that self-assembles into vesicles or nanotubes was described in 2008, 18 and more recently Guldi, Torres, Bottari and coworkers reported a remarkable exciplex emission due to intramolecular interactions between a fluorinated subphthalocyanine and an aniline fragment spatially arranged by the distorted TCBD unit, 19 while another report proposed urea-based TCBDs as luminophores. 20 In the light of these studies, it appears that TCBDs offer more intriguing potentialities than initially foreseen that have yet to be explored.…”