Naslov
Substituent effect on conformational preference and anion binding of thiourea receptors

Autori
Trošelj, Pavle ; Briš, Anamarija ; Margetić, Davor

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, ostalo

Izvornik
Challenges in Organic Chemistry ISACS14 / - Shanghai, 2014

Skup
ISACS 14 Challenges in Organic Chemistry

Mjesto i datum
Šangaj, Kina, 07.08.2014. - 10.08.2014

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
thiourea; conformation; hydrogen bond

Sažetak
In the last decade non-covalent interactions of thioureas have drawn significant attention of scientific community. Due to its double hydrogen bond (HB) donation thioureas have been frequently used in organic chemistry specially in the fields of organocatalysis, 1 anion recognition, 2 and transport.3 Despite strong HB donation thioureas suffer from two major drawbacks when used as molecular hosts. One is propensity to deprotonate, especially in polar media and with more basic anion.4 The other is the fact that Z, E conformation which is unfavourable for double hydrogen bond donation is usually more stable than Z, Z conformation. In this study we wanted to explore how substitution in para- position of aryl ring influences conformational preference and how that translates to anion binding of N’-alkyl-N’’-aryl thioureas. Single crystal X-ray diffraction experiments indicated that appending more electron withdrawing groups (EWG) shifts preference towards more preorganized Z, Z conformer. Quantum chemical (DFT) calculations agreed well with experimental findings and gave an explanation for the observed trend. Equilibrium binding constants for anions of different shape and size were determined experimentally by using UV-vis and 1H NMR titrations. Experimental results were complemented with theoretical and showed that influence of substituent is twofold. Beside enhancement of acidity of NH-protons with more EWG, due to observed conformational changes upon binding, initial conformation of thiourea group also contributes to binding strength. Results also prove that weaker interaction between receptor and substrate means reduced substituent effect on binding strength.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

POVEZANOST RADA