精品论文Multisensing Anion Recognition with thioure basedReceptor functionalized with tetrathiafulvalene Unit 1Chang Su, Liying Gu, Bingzhu Yin*Key Laboratory of Organism Functional Factors of the Changbai Mountain, Yanbian University, Ministry of Education, Yanji 133002, P.R. Chinazqcongybu.edu.cnAbstractA series thiourea/urea-based anion receptors functionalized with tetrathiafulvalene(1-4) were prepared. Among them, 4 displays the high sensitive multisensing for acetate anion over various anions in acetonitrile with dramatic changes in UV-vis spectra , cyclic voltammogram and 1H NMR spectra. Conformation change induced by anion complexing of 4 caused the improvement of ICT channel to enhance the charge transfer not noly from thiourea moiety but also from TTF unit to electron-defect benzene ring. TTF unit plays a synergic charge transfer role for trifluoromethyl group in the ICT process. DFT calculation supported the hypothesis of conformational change and ICT channel improvement.Keywords: tetrathiafulvalene; anion receptor; thiourea; multisensing; recognition1IntroductionIn recent years, the field of anion recognition associated with the signaling of reversible anion binding using synthetic chemosensors, stimulated by Simmons and Parks report in 1968 1, has witnessed increasing popularity and considerable efforts have been made to design chemosensors for anions since anions play a fundamental role in a wide range of chemical and biological processes 2-6. One of the most co-mmom modes of signal transduction is electrochemical-based changes in the sensor incurred by association of the analyte with the receptor 7. The tetrathiafulvalene is a strong - electron donor and an ideal redox-active sensing unit and its oxidation to the radical cation (TTF+) and dication(TTF2+) occurring sequentially and reversibly in a desirable range, but there are only a few example of anion receptor incorporating a TTF unit that are capable of multisensing so far 8-14.It is well known that urea/thiourea functional groups are among the most popular binding motifs currently being used to prepare neutral anion-binding receptors because of they provide two hydrogen-bond donor groups that point in same direction and which are spaced appropriately to interact with a range of anionic substrates 15-21. It is well performanced that the N-benzamidothioureas showed a dramatically increased anion affinity compared with N-benzoylthioureas and N-phenylthioureas due to anion binding induced N-N conformational change and the resultant intramolecular charge transfer (ICT) in the anion binding complex 22-28. In order to explore the role of TTF unit in ICT process, we synthesized four N-(6,7-dibutylthio- tetrathiafulvaleno2,3-c-pyrrole-2-amido)-N-arylurea/thiourea deriva-tives (1-4) (Fig. 1) and eveluated their anion binding affinity.1We thank the National Natural Science Foundation of China (Grant 20662010) , the Specialized Research Fund for the Doctoral Program of Higher Education ( Grant 20060184001) and the open project of State Key Laboratory of Supramolecular Structure and Materials for financial support.-1-2Results and discussionAmong these receptors, only the receptor 4, as the increased acidity of the NH bonds result from that more acidic thiourea than urea and the intense electron-withdrawing character of trifluoromethyl groupBuS S SBuS S SN TsLDA/ClCOOMeTHF, 75%BuS S SBuS S SN TsMeONaMeOH/THF5 6 COO Me89%BuS S SBuS S S222H N NHH ON HEtOH, 95%BuS S SNHBuS S SRNCXDMF7 COO Me8 CONHNH2BuS S BuSSSNH SNH X OHN1:X = O ,R = H(68%) HN2:X = O ,R = CF3 (74%) R3:X = S, R =H (77%)4:X = S, R = CF3 (80%)Fig 1 Synthesis route of 1-429-30, displays the multisensing for acetate anion over various anions in acetonitrile with dramatic changes in UV-vis spectra , cyclic voltammogram and 1H NMR. The conformation change induced by anion complexing of 4 caused the improvement of ICT channel which enhanced the charge transfer not noly from thiourea moiety but also from TTF unit to electron-defect benzene ring. As expected, TTF unit plays a synergic charge transfer role for trifluoromethyl group in the ICT process.First of all, we investigated the effects of various anions on the absorption spectrum of receptor 4. Addition of AcO-, as tetrabutylammonium salts to solutions of compound 4 in acetonitrile resulted in dramatic changes in the UV-vis spectra of the receptor with an increase as well as red-shift of the absorbance in the328 nm and a disappearance of absorbance in the 237 nm region, respectively (Fig. 1). The appearance of three isosbestic points at approximately 225, 250 and 297 nm, respectively, point to the formation of well-defined anion binding complex