Department of Chemistry, Mississippi State University, Mississippi State, MS 39762, USA.
Department of Chemistry, Physics and Atmospheric Sciences, Jackson State University, Jackson, MS 39217, USA.
Molecules. 2023 Jun 22;28(13):4929. doi: 10.3390/molecules28134929.
NIR dyes have become popular for many applications, including biosensing and imaging. For this reason, the molecular switch mechanism of the xanthene dyes makes them useful for in vivo detection and imaging of bioanalytes. Our group has been designing NIR xanthene-based dyes by the donor-acceptor-donor approach; however, the equilibrium between their opened and closed forms varies depending on the donors and spacer. We synthesized donor-acceptor-donor NIR xanthene-based dyes with an alkyne spacer via the Sonogashira coupling reaction to investigate the effects of the alkyne spacer and the donors on the maximum absorption wavelength and the molecular switching (ring opening) process of the dyes. We evaluated the strength and nature of the donors and the presence and absence of the alkyne spacer on the properties of the dyes. It was shown that the alkyne spacer extended the conjugation of the dyes, leading to absorption wavelengths of longer values compared with the dyes without the alkyne group. In addition, strong charge transfer donors shifted the absorption wavelength towards the NIR region, while donors with strong π-donation resulted in xanthene dyes with a smaller equilibrium constant. DFT/TDDFT calculations corroborated the experimental data in most of the cases. containing the N,N-dimethylaniline group gave contrary results and is being further investigated.
近红外染料由于在生物传感和成像等诸多领域的应用而受到广泛关注。鉴于此，香豆素染料的分子开关机制使它们可用于生物分析物的体内检测和成像。本课题组一直采用给体-受体-给体策略设计近红外香豆素基染料；然而，其开环和闭环形式之间的平衡会因给体和间隔基的不同而发生变化。我们通过 Sonogashira 偶联反应合成了带有炔基间隔基的给体-受体-给体近红外香豆素基染料，以研究炔基间隔基和给体对染料最大吸收波长和分子开关（开环）过程的影响。我们评估了供体的强度和性质以及炔基间隔基的存在与否对染料性质的影响。结果表明，炔基间隔基扩展了染料的共轭，使得其吸收波长与不含炔基的染料相比值更长。此外，强电荷转移供体使吸收波长向近红外区域移动，而具有强π-供电子能力的供体则使香豆素染料的平衡常数更小。DFT/TDDFT 计算在大多数情况下证实了实验数据。含有 N,N-二甲基苯胺基团的染料给出了相反的结果，目前正在进一步研究。
