Costa Ana L, Monteiro Rodrigo P, Nunes Barradas Paulo D, Ferreira Simone C R, Cunha Carla, Gomes Ana C, Gonçalves Isabel S, Seixas de Melo J Sérgio, Pillinger Martyn
Department of Chemistry, CICECO-Aveiro Institute of Materials, University of Aveiro, Aveiro, Portugal.
Coimbra Chemistry Centre (CQC)-IMS, Department of Chemistry, University of Coimbra, Coimbra, Portugal.
Front Chem. 2022 Oct 10;10:1004586. doi: 10.3389/fchem.2022.1004586. eCollection 2022.
A ketodiacid, 4,4'-dicarboxylate-dicumyl ketone (), has been intercalated into a Zn, Al layered double hydroxide (LDH) by a coprecipitation synthesis strategy. The structure and chemical composition of the resultant hybrid material (LDH-KDA3) were characterized by powder X-ray diffraction (PXRD), FT-IR, FT-Raman and solid-state C{H} NMR spectroscopies, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TGA), and elemental analysis (CHN). PXRD showed that the dicarboxylate guest molecules assembled into a monolayer to give a basal spacing of 18.0 Å. TGA revealed that the organic guest starts to decompose at a significantly higher temperature (ca. 330°C) than that determined for the free ketodiacid (ca. 230°C). Photochemical experiments were performed to probe the photoreactivity of the ketoacid in the crystalline state, in solution, and as a guest embedded within the photochemically-inert LDH host. Irradiation of the bulk crystalline ketoacid results in photodecarbonylation and the exclusive formation of the radical-radical combination product. Solution studies employing the standard myoglobin (Mb) assay for quantification of released CO showed that the ketoacid behaved as a photoactivatable CO-releasing molecule for transfer of CO to heme proteins, although the photoreactivity was low. No photoinduced release of CO was found for the LDH system, indicating that molecular confinement enhanced the photo-stability of the hexasubstituted ketone. To better understand the behavior of under irradiation, a more comprehensive study, involving excitation of this compound in DMSO-d followed by H NMR, UV-Vis and fluorescence spectroscopy, was undertaken and further rationalized with the help of time-dependent density functional theory (TDDFT) electronic quantum calculations. The photophysical study showed the formation of a less emissive compound (or compounds). New signals in the H NMR spectra were attributed to photoproducts obtained Norrish type I α-cleavage decarbonylation and Norrish type II (followed by CH migration) pathways. TDDFT calculations predicted that the formation of a keto-enol system ( a CH migration step in the type II pathway) was highly favorable and consistent with the observed spectral data.
一种酮二酸，4,4'-二羧基二苯甲酮（ ），已通过共沉淀合成策略插层到锌铝层状双氢氧化物（LDH）中。通过粉末X射线衍射（PXRD）、傅里叶变换红外光谱（FT-IR）、傅里叶变换拉曼光谱、固态碳氢核磁共振光谱、扫描电子显微镜（SEM）、能量色散X射线光谱（EDS）、热重分析（TGA）和元素分析（CHN）对所得杂化材料（LDH-KDA3）的结构和化学成分进行了表征。PXRD表明二羧酸盐客体分子组装成单层，基间距为18.0 Å。TGA显示有机客体开始分解的温度（约330°C）明显高于游离酮二酸的分解温度（约230°C）。进行了光化学实验，以探究酮酸在结晶态、溶液态以及作为嵌入光化学惰性LDH主体中的客体时的光反应活性。块状结晶酮酸的辐照导致光脱羰反应，并专一形成自由基-自由基结合产物。采用标准肌红蛋白（Mb）测定法对释放的CO进行定量的溶液研究表明，尽管光反应活性较低，但酮酸表现为一种可光活化的CO释放分子，用于将CO转移至血红素蛋白。未发现LDH体系有光诱导的CO释放，这表明分子限域增强了六取代酮的光稳定性。为了更好地理解 在辐照下的行为，进行了一项更全面的研究，包括在氘代二甲亚砜中激发该化合物，随后进行氢核磁共振、紫外可见光谱和荧光光谱分析，并借助含时密度泛函理论（TDDFT）电子量子计算进行了进一步的合理解释。光物理研究表明形成了一种发射性较弱的化合物（或多种化合物）。氢核磁共振谱中的新信号归因于通过Norrish I型α-裂解脱羰和Norrish II型（随后是CH迁移）途径获得的光产物。TDDFT计算预测酮-烯醇体系的形成（II型途径中的CH迁移步骤）非常有利，且与观察到的光谱数据一致。
