The chemical reaction of 2-(methylsulfinyl)naphtho[2,3-d]thiazole-4,9-dione (3) using different amines, including benzylamine (4a), morpholine (4b), thiomorpholine (4c), piperidine (4d), and 4-methylpiperazine (4e), produced corresponding new tricyclic naphtho[2,3-d]thiazole–4,9–dione compounds (5a–e) in moderate-to-good yields. The photophysical properties and antimicrobial activities of these compounds (5a–e) were then characterized. Owing to the extended π-conjugated system of naphtho[2,3-d]thiazole–4,9–dione skeleton and substituent effect, 5a–e showed fluorescence both in solution and in the solid state. The introduction of nitrogen-containing heterocycles at position 2 of the thiazole ring on naphtho[2,3-d]thiazole-4,9-dione led to large bathochromic shifts in solution, and 5b–e exhibited orange-red fluorescence with emission maxima of over 600 nm in highly polar solvents. Staphylococcus aureus (S. aureus) is a highly pathogenic bacterium, and infection with its antimicrobial-resistant pathogen methicillin-resistant S. aureus (MRSA) results in serious clinical problems. In this study, we also investigated the antimicrobial activities of 5a–e against S. aureus, MRSA, and S. epidermidis. Compounds 5c with thiomorpholine group and 5e with 4-methylpiperazine group showed potent antimicrobial activity against these bacteria. These results will lead to the development of new fluorescent dyes with antimicrobial activity in the future.

中文翻译：

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荧光萘并[2,3-d]噻唑-4,9-二酮的合成、光物理表征及其对葡萄球菌的抗菌活性


2-(甲基亚磺酰基)萘并[2,3-d]噻唑-4,9-二酮(3)使用不同胺，包括苄胺(4a)、吗啉(4b)、硫代吗啉(4c)、哌啶(4d)的化学反应）和4-甲基哌嗪（4e），以中等至良好的产率产生相应的新型三环萘并[2,3-d]噻唑-4,9-二酮化合物（5a-e）。然后对这些化合物 (5a-e) 的光物理性质和抗菌活性进行了表征。由于萘并[2,3-d]噻唑-4,9-二酮骨架的扩展π-共轭体系和取代基效应，5a-e在溶液和固态下均显示出荧光。在萘并[2,3-d]噻唑-4,9-二酮的噻唑环2位引入含氮杂环导致溶液中出现较大的红移，5b-e表现出发射最大值的橙红色荧光在高极性溶剂中超过 600 nm。金黄色葡萄球菌（S. aureus）是一种高致病性细菌，其抗菌病原体耐甲氧西林金黄色葡萄球菌（MRSA）的感染会导致严重的临床问题。在这项研究中，我们还研究了 5a-e 对金黄色葡萄球菌、MRSA 和表皮葡萄球菌的抗菌活性。具有硫代吗啉基团的化合物5c和具有4-甲基哌嗪基团的化合物5e对这些细菌表现出有效的抗菌活性。这些结果将导致未来具有抗菌活性的新型荧光染料的开发。