Squaraine Compounds: Tailored Design and Synthesis towards a Variety of Material Science Applications

Abstract

The interest in squaraine compounds, a relatively old class of dyes, has been recently renewed due to their potential usefulness in a large number of technologically relevant fields such as two-photon absorbing materials, field-effect transistors, solar cells, NIR-emitting fluorescent probes and sensitizers for photodynamic therapy. Aim of the present review is to summarize the most convenient strategies for squaraines and polysquaraines syntheses and to discuss the design strategies enabling for the preparation of squaraines having properties relevant for a given material application. In particular, in the first section of the review we will describe the various synthetic approaches for the preparation of squaraine and polysquaraine derivatives. The second section will

A hybrid CMOS-imager with a solution-processable polymer as photoactive layer

“…The major strength of the hybrid concept is the portability to different solutionprocessable photoactive materials. To demonstrate the ease of switching the material system to extend the absorption to the NIR region, we added a SQ dye 12,[44][45][46] as additional donor material to the PCBM:P3HT solution to exploit the absorption spectrum of SQ between 600 and 900 nm. About solar cells and photodetectors with a bulk-heterojunction active layer of PCBM:SQ, it was already reported [44][45][46] .…”

“…In addition, various organic materials absorbing at different wavelengths can be integrated in the photodetector. For the visible range of the spectrum, a bulk-heterojunction of PCBM:P3HT (poly(3-hexylthiophene): [6,6]-phenyl C61 butyric acid methylester) (refs 9, 10) can be employed for photodetection 11 or squaraine (SQ) 12 for a near-infrared (NIR)-enhanced absorption. High performance and low-cost polymer photodetectors can also be realized beyond the absorption edge of silicon at 1.1 mm competing with resource-limited and costly InGaAs photodiodes 13 .…”

Exciton Transport in Molecular Aggregates – From Natural Antennas to Synthetic Chromophore Systems

“…The superior optical properties (narrow and strong absorption in the red to near-infrared spectral region, high fluorescence quantum yield) together with their structural diversity make them ideal dyes for numerous optical applications (biolabelling, data storage, ion sensing, photosensitizers in electrophotography, nonlinear optics) but also for more fundamental investigations. [206][207][208][209][210][211][212][213][214][215][216][217] In this section we concentrate on squaraine dyes that are formed from the condensation reaction of indolenine donors with squaric acid or their derivatives. These indolenine squaraine dyes may be used to build up not only linear and branched oligomers but also polymers.…”

Aminosquaraines as potential photodynamic agents: Synthesis and evaluation of in vitro cytotoxicity

“…As a result, a lot of work has been published on the structural variation of squaraines which, however, has been mainly focused on the variation of the nature and substitution of the heterocyclic terminal groups [11]. The derivatization of the central squaric core, on the other hand, has been poorly addressed and has been the focus of our research for some years [12][13][14].…”