Heterohalkalı tiyazolo tiyazol bileşiklerininsentezi ve spektroskopik özellikleri
Synthesis and spectroscopic properties of heterocyclic thiazolo thiazole compounds
- Tez No: 1018543
- Danışmanlar: PROF. DR. UĞURSOY OLGUN
- Tez Türü: Doktora
- Konular: Kimya, Chemistry
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 2026
- Dil: Türkçe
- Üniversite: Sakarya Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Kimya Ana Bilim Dalı
- Bilim Dalı: Fizikokimya Bilim Dalı
- Sayfa Sayısı: Belirtilmemiş.
Özet
Tiyazol türevleri; optik, elektronik ve biyolojik özellikleri sayesinde geniş bir uygulama alanına sahip heterosiklik bileşiklerdir. Bazı tiyazol yapılı moleküller biyolojik etkinlikleri nedeniyle ilaç geliştirme çalışmalarında değerlendirilirken, bazıları da optik sensörler ve fonksiyonel malzemeler gibi teknolojik uygulamalarda önemli rol oynamaktadır. Işığa duyarlı davranışları, özellikle çevresel analizlerde ve biyolojik örneklerin izlenmesinde kullanılan floresans tabanlı sensörlerin tasarımında değerli bir avantaj sunmaktadır. Bu tez çalışmasında, asimetrik tiyazolo[5,4-d] tiyazol türevlerinin sentezi ve karakterizasyonu üzerinde yoğunlaşılmıştır. Asimetrik yapıların, moleküllere gelişmiş optik ve elektronik özellikler kazandırdığı bilinmektedir. Bu nedenle, sentezlenen bileşiklerin farklı çözücülerdeki davranışları, solvatokromik özellikleri ve floresans karakteristikleri detaylı olarak incelenmiştir. Solvatokromizm, bileşiklerin hem emilim hem de emisyon bantlarını etkilediğinden, potansiyel uygulamalar açısından kritik bir parametre olarak ele alınmıştır. Sentez bölümünde, simetrik ve asimetrik tiyazolo-tiyazol türevlerinin çift yoğunlaşma reaksiyonları ile elde edilme yöntemleri verilmiş; ardından seçili moleküller, polibenzoksazin polimer matrisi ile modifiye edilerek yeni hibrit yapılar oluşturulmuştur. Bu polimer-türevli sistemlerin literatürdeki benzer çalışmalarla karşılaştırmalı değerlendirmeleri yapılmıştır. Çalışmada sentezlenen tüm özgün bileşiklerin yapısal doğrulaması, UV/Vis, FTIR, ESI-MS, floresans spektroskopisi, SEM/EDS, döngüsel voltametri (CV) ve MALDI-TOF kütle spektrometrisi gibi ileri analitik tekniklerle kapsamlı bir şekilde yapılmıştır. Ayrıca sentezlenen bazı bileşiklerin antibakteriyel aktiviteleri de değerlendirilmiş ve biyolojik potansiyelleri ortaya konmuştur. Tiyazolo[5,4-d] tiyazol (TT) çekirdeği, iki heteroatom (N ve S) içeren kaynaşmış aromatik yapısı sayesinde yüksek konjugasyon, ayarlanabilir elektronik seviyeler ve belirgin fotofiziksel yanıtlar sunan önemli bir heterohalkalı platformdur. Bu tez çalışması, özellikle asimetrik TT türevlerinin rasyonel tasarımı, sentezi ve çok yönlü karakterizasyonuna odaklanmış; elde edilen bileşiklerin optik–elektronik davranışları ile seçili örneklerin antibakteriyel potansiyeli birlikte değerlendirilmiştir. Sentez çalışmaları, ditiyooksamit ile aromatik aldehitlerin 1:2 mol oranında çift yoğunlaşma reaksiyonu üzerinden yürütülmüş; bazik ortamda (NaOH) gerçekleştirilen reaksiyonun ardından nötralizasyon (HCl), ekstraksiyon ve çözücü uzaklaştırma adımlarıyla sarı–turuncu tonlarda ürünler elde edilmiştir. Bu yaklaşım, tez boyunca kullanılan simetrik ve asimetrik TT türevleri için temel sentez omurgasını oluşturmuştur. Elde edilen özgün yapıların doğrulanmasında UV-Vis ve floresans spektroskopisi ile çözücüye bağlı bant kaymaları izlenerek solvatokromik/ICT karakteri yorumlanmış; FTIR ile karakteristik fonksiyonel grup titreşimleri desteklenmiş; döngüsel voltametri (CV) ile redoks davranışı incelenmiştir. Ayrıca HRMS (ESI) ve MALDI-TOF ölçümleri, hedef yapılarla uyumlu m/z sinyalleriyle kütle doğrulaması sağlamıştır: örneğin s-TT1 için m/z 299.1519, s-TT2 için m/z 326.1371 ve as-TT3 için m/z 351.1266 sinyalleri raporlanmış; genel olarak HRMS bulgularının beklenen kütlelerle uyumlu olduğu belirtilmiştir. Yüzey ve mikroyapı incelemeleri için FE-SEM/EDS kullanılarak morfoloji ve elementel dağılım değerlendirilmiştir. Biyolojik açıdan, sentezlenen TT türevlerinin antibakteriyel aktiviteleri E. coli ve S. aureus suşlarına karşı disk difüzyon yöntemiyle taranmıştır. Sonuçlar, asimetrik yapıların genel olarak daha iyi bir profil sunabildiğini göstermiştir: as-TT3 S. aureus'a karşı 15 mm, as-TT2 12 mm ve as-TT15 her iki suşa karşı 12/12 mm inhibisyon zonu vermiştir. Simetrik örneklerden s-TT2 özellikle S. aureus'a karşı 17 mm ile dikkat çekmiş; buna karşın as-TT12 ve s-TT3 gibi bazı bileşiklerde belirgin zon gözlenmemiştir. Kontrollerle kıyaslandığında berberin 15/15 mm, triklosan ise 28/32 mm zon çaplarıyla daha yüksek aktivite göstermiştir. Bu bütüncül yaklaşım sayesinde, TT türevlerinde yapı–özellik ilişkisi hem spektroskopik/elektrokimyasal kanıtlarla hem de seçili biyolojik testlerle desteklenmiş; özellikle asimetrik tasarımın optik yanıtı çeşitlendirme ve bazı koşullarda antibakteriyel etkiyi iyileştirme potansiyeli ortaya konmuştur.
Özet (Çeviri)
Thiazole derivatives are heterocyclic compounds with a wide range of applications due to their optical, electronic, and biological properties. While some thiazole-structured molecules are evaluated in drug development studies due to their biological activity, others play an important role in technological applications such as optical sensors and functional materials. Their light-sensitive behavior offers a valuable advantage, especially in the design of fluorescence-based sensors used in environmental analysis and monitoring of biological samples. This thesis focuses on the synthesis and characterization of asymmetric thiazolo[5,4-d] thiazole derivatives. Asymmetric structures are known to impart enhanced optical and electronic properties to molecules. Therefore, the behavior of the synthesized compounds in different solvents, their solvatochromic properties, and fluorescence characteristics were investigated in detail. Solvatochromism was considered a critical parameter in terms of potential applications, as it affects both the absorption and emission bands of the compounds. In the synthesis section, methods for obtaining symmetric and asymmetric thiazolo-thiazole derivatives via double condensation reactions are given; Subsequently, selected molecules were modified with a polybenzoxazine polymer matrix to create novel hybrid structures. Comparative evaluations of these polymer-derived systems were conducted with similar studies in the literature. Structural validation of all original compounds synthesized in this study was carried out extensively using advanced analytical techniques such as UV/Vis, FTIR, HRMS, fluorescence spectroscopy, SEM/EDS, cyclic voltammetry (CV), and MALDI-TOF mass spectrometry. Furthermore, the antibacterial activities of some of the synthesized compounds were evaluated, and their biological potential was revealed. The thiazolo[5,4-d] thiazole (TT) core is an important heterocyclic platform offering high conjugation, tunable electronic levels, and pronounced photophysical responses thanks to its fused aromatic structure containing two heteroatoms (N and S). This thesis focuses particularly on the rational design, synthesis, and versatile characterization of asymmetric TT derivatives; The opto-electronic behavior of the obtained compounds and the antibacterial potential of selected samples were evaluated together. Synthesis studies were carried out via a double condensation reaction of dithiooxamide with aromatic aldehydes in a 1:2 molar ratio; following the reaction performed in a basic medium (NaOH), neutralization (HCl), extraction, and solvent removal steps yielded yellow-orange colored products. This approach formed the basic synthesis backbone for the symmetric and asymmetric TT derivatives used throughout the thesis. In the validation of the obtained unique structures, solvatochromic/ICT character was interpreted by monitoring solvent-dependent band shifts with UV-Vis and fluorescence spectroscopy; characteristic functional group vibrations were supported by FTIR. Furthermore, ESI-MS and MALDI-TOF measurements provided mass validation with m/z signals consistent with target structures: for example, m/z 299.1519 for s-TT1, m/z 326.1371 for s-TT2, and m/z 351.1266 for as-TT3 were reported; overall, the HRMS findings were consistent with the expected masses. Morphology and elemental distribution were evaluated using FE-SEM/EDS for surface and microstructure investigations. Biologically, the antibacterial activities of the synthesized TT derivatives were screened against E. coli and S. aureus strains using the disk diffusion method. The results showed that asymmetric structures generally provided a better profile: as-TT3 yielded a 15 mm inhibition zone against S. aureus, as-TT2 a 12 mm zone, and as-TT15 a 12/12 mm zone against both strains. Among the symmetrical samples, s-TT2 was particularly noteworthy against S. aureus with a zone diameter of 17 mm; however, some compounds such as as-TT12 and s-TT3 did not show distinct zones. Compared to controls, berberine showed higher activity with zone diameters of 15/15 mm, and triclosan with zone diameters of 28/32 mm. Thanks to this holistic approach, the structure-property relationship in TT derivatives was supported by both spectroscopic/electrochemical evidence and selected biological tests; in particular, the potential of asymmetric design to diversify the optical response and improve antibacterial activity under certain conditions was demonstrated. This dissertation expands the chemical space of thiazolo[5,4-d]thiazole (TTz) chromophores by systematically varying symmetry (symmetric vs. asymmetric), terminal aromatic units (phenyl, naphthyl, indolyl), and polymer-integrated architectures. The central design hypothesis was that breaking symmetry and/or extending π-conjugation would increase intramolecular charge transfer (ICT) contribution, amplify solvatochromic response, and enable fine control over frontier orbital energies (HOMO/LUMO) relevant to optoelectronic and sensing applications. In the synthetic part of the study, TTz scaffolds were obtained through the double condensation of dithiooxamide with aromatic aldehydes (1:2 molar ratio) under basic conditions (NaOH), followed by neutralization (HCl), extraction, and solvent removal. The method proved robust across structurally diverse aldehydes and yielded intensely colored products (yellow–orange), consistent with the formation of extended conjugated systems. Symmetric dyes (s‑TT1, s‑TT2, s‑TT3, s‑TT10, s‑TT12) and asymmetric dyes (as‑TT1, as‑TT2, as‑TT3, as‑TT11, as‑TT15) were prepared as a comparative set, allowing direct assessment of structure–property relationships. Comprehensive structural confirmation was achieved by combining vibrational, electronic, mass, and electrochemical evidence. FTIR spectra supported the presence of characteristic functional groups in the target products, while HRMS (ESI) and MALDI‑TOF provided unambiguous mass validation. Representative high‑resolution signals reported in this thesis include m/z 299.1519 (s‑TT1), m/z 326.1371 (s‑TT2), and m/z 351.1266 (as‑TT3), which were consistent with the calculated molecular ions. In addition, FE‑SEM imaging and EDS analysis enabled the examination of morphology and elemental distribution, supporting the formation of homogeneous microstructures for both small molecules and polymeric materials. Optical characterization by UV–Vis absorption and fluorescence spectroscopy emphasized the strong dependence of the electronic transitions on conjugation length, donor/acceptor balance, and molecular asymmetry. In THF, the absorption maxima of the TTz dyes spanned a broad region (355–465 nm for the selected symmetric set and 365–465 nm for the asymmetric set), reflecting tunable π–π* and ICT-related transitions. The red‑shifted absorptions observed for more extended/heteroaromatic termini were consistent with a narrowed optical band gap and enhanced charge‑transfer character. Solvent-dependent band shifts in both absorption and emission indicated a measurable solvatochromic response, which is highly relevant for sensor applications in complex media where polarity and hydrogen-bonding ability can change. The optoelectronic consequences of structural variation were further quantified using optical band-gap estimations (Eg) derived from UV–Vis onset behavior. The symmetric series exhibited Eg values of 2.40–2.97 eV (e.g., 2.97 eV for s‑TT1 and 2.40 eV for s‑TT12), whereas the asymmetric series covered 2.12–2.80 eV (notably 2.12 eV for as‑TT15 and 2.80 eV for as‑TT1). These results demonstrate that asymmetric design and π-extension can provide access to lower band gaps within the same TTz core, offering a practical strategy for tailoring light-harvesting windows and energy-level alignment in organic electronic devices. In addition to discrete dyes, selected TTz units were integrated into polybenzoxazine (PBZ) and fluoro‑polybenzoxazine (FPBZ) frameworks to obtain hybrid functional materials. The polymer-bound systems retained optical activity and enabled further tuning via chemical modification with cyanoacrylic acid (SAA) and boron subphthalocyanine (SubPc) fragments. Microwave-assisted post‑functionalization produced highly conjugated hybrid materials with red‑shifted absorption around 562–563 nm and band gaps concentrated in the 2.15–2.20 eV range (e.g., FPBZ‑SAA‑150/Cl‑B‑SubPc and FPBZ‑SAA‑150/as‑TT15 hybrids), indicating successful electronic coupling and extended delocalization in the macromolecular environment. Cyclic voltammetry complemented the optical analyses by providing redox-based insights into frontier orbital levels. Together with the optical band-gap trends, the electrochemical data supported the conclusion that electronic asymmetry and conjugation expansion modulate the charge-transport-relevant energy landscape of TTz systems. Such tunability is valuable for designing TTz-derived components for dye-sensitized solar cells (DSSCs), organic photovoltaics (OPVs), OLED emitters, and fluorescence-based chemical sensors. Finally, the biological screening highlighted the potential of TTz derivatives as antibacterial candidates. Disk diffusion assays against E. coli (Gram-negative) and S. aureus (Gram-positive) revealed compound-dependent activity profiles. Quantitatively, as‑TT2 and as‑TT3 produced inhibition zones of 10 mm (E. coli) and 12–15 mm (S. aureus), while as‑TT15 showed 12/12 mm activity against both strains. Among the symmetric dyes, s‑TT2 was notable with a 17 mm zone against S. aureus (and 9 mm against E. coli). Compared with the positive controls, berberine gave 15/15 mm and triclosan showed 28/32 mm (E. coli/S. aureus). These results suggest that TTz-based scaffolds can be further optimized through rational substitution (polarity, aromatic extension, and functional group selection) to enhance bacterial membrane interaction and overall potency. Overall, this thesis demonstrates that TTz chemistry enables an integrated molecular-to-materials strategy: (i) reliable synthesis of symmetric and asymmetric TTz dyes, (ii) multi-technique structural confirmation, (iii) tunable photophysical and electrochemical properties that track with conjugation and asymmetry, (iv) polymeric and microwave-assisted hybridization to push absorption into the visible-red region, and (v) measurable antibacterial effects for selected structures. The combined dataset provides a foundation for future work targeting optimized TTz-based sensors, optoelectronic components, and bioactive materials
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