Synthesis of phthalimides cross-conjugated with an azulene ring, and their structural, optical and electrochemical properties

Azulene-Substituted Donor-Acceptor Polymethines and 1,6'-Bi-, 1,6';3,6''-Ter-, and Quinqueazulenes via Zincke Salts: Synthesis, and Structural, Optical, and Electrochemical Properties

Azulene-substituted donor-acceptor polymethines, bi-, ter-, and quinqueazulenes composed of the 1,6'-biazulene unit have been successfully prepared from corresponding Zincke salts. The synthesis of polymethines through the reaction of Zincke salts with several amines, followed by a Knoevenagel reaction with malononitrile, was accomplished in moderate to high yields (40-92 %). Meanwhile, the reaction of Zincke salts with secondary amines and the subsequent sequential condensation-cyclization with cyclopentadienide ions, so-called Ziegler-Hafner method, produced the corresponding 1,6'-biazulenes, 1,6';3,6''-terazulenes, and quinqueazulene, respectively. The structural, optical, and electrochemical properties of the azulene-substituted donor-acceptor polymethines, bi-, ter-, and quinqueazulenes were revealed by single-crystal X-ray structure analysis, UV/vis spectroscopy, voltammetry analysis, spectroelectrochemistry, and theoretical calculations. These results suggested that the substituents on the azulene ring and their substitution positions directly affect their reactivities, optical and electrochemical properties.

Azulene-A Bright Core for Sensing and Imaging

Azulene is a hydrocarbon isomer of naphthalene known for its unusual colour and fluorescence properties. Through the harnessing of these properties, the literature has been enriched with a series of chemical sensors and dosimeters with distinct colorimetric and fluorescence responses. This review focuses specifically on the latter of these phenomena. The review is subdivided into two sections. Section one discusses turn-on fluorescent sensors employing azulene, for which the literature is dominated by examples of the unusual phenomenon of azulene protonation-dependent fluorescence. Section two focuses on fluorescent azulenes that have been used in the context of biological sensing and imaging. To aid the reader, the azulene skeleton is highlighted in blue in each compound.

Beyond conventional construction of the phthalimide core: a review

This review highlights (2010–2021) different strategies for the construction of the phthalimide core apart from traditional synthetic routes.

Development of Heterocycle-Substituted and Fused Azulenes in the Last Decade (2010-2020)

Azulene derivatives with heterocyclic moieties in the molecule have been synthesized for applications in materials science by taking advantage of their unique properties. These derivatives have been prepared by various methods, involving electrophilic substitution, condensation, cyclization, and transition metal-catalyzed cross-coupling reactions. Herein, we present the development of the synthetic methods, reactivities, and physical properties for the heterocycle-substituted and heterocycle-fused azulenes reported in the last decade.

Two Isomeric Azulene-Decorated Naphthodithiophene Diimide-based Triads: Molecular Orbital Distribution Controls Polarity Change of OFETs Through Connection Position

Altering the charge carrier transport polarities of organic semiconductors by molecular orbital distribution has gained great interest. Herein, we report two isomeric azulene-decorated naphthodithiophene diimide (NDTI)-based triads (e.g., NDTI-B2Az and NDTI-B6Az), in which two azulene units were connected with NDTI at the 2-position of the azulene ring in NDTI-B2Az, whereas two azulene units were incorporated with NDTI at the 6-position of the azulene ring in NDTI-B6Az. The two isomeric triads were excellently soluble in common organic solvents. Density functional theory calculations on the molecular orbital distributions of the triads reveal that the lowest unoccupied molecular orbitals are completely delocalized over the entire molecule for both NDTI-B2Az and NDTI-B6Az, indicating great potential for n-type transport behavior, whereas the highest occupied molecular orbitals are mainly delocalized over the entire molecule for NDTI-B2Az or only localized at the two terminal azulene units for NDTI-B6Az, implying great potential for p-type transport behavior for the former and a disadvantage of hole carrier transport for the latter. Under ambient conditions, solution-processed bottom-gate top-contact transistors based on NDTI-B2Az showed ambipolar field-effect transistor (FET) characteristics with high electron and hole mobilities of 0.32 (effective electron mobility ≈0.14 cm² V^-1 s^-1 according to a reliability factor of 43%) and 0.03 cm² V^-1 s^-1 (effective hole mobility ≈0.01 cm² V^-1 s^-1 according to a reliability factor of 33%), respectively, whereas a typically unipolar n-channel behavior is found for a film of NDTI-B6Az with a high electron mobility up to 0.13 cm² V^-1 s^-1 (effective electron mobility ≈0.06 cm² V^-1 s^-1 according to a reliability factor of 43%). The results indicate that the polarity change of organic FETs based on the two isomeric triads could be controlled by the molecular orbital distributions through the connection position between the azulene unit and NDTI.