Imidazolium silanethiolates relevant to the active site of cysteine proteases. A cooperative effect in a chain of NH+⋯S− hydrogen bonds

Abstract

Three imidazolium silanethiolates relevant to the active site of cysteine proteases have been synthesized and investigated by X-ray diffraction, IR spectroscopy and computational methods. As indicated by crystallographic and FT-IR data in the solid state, the transfer of proton from thiol to imidazole takes place and a thiolato-imidazolium ion pair is formed. The FT-IR spectra of crystalline imidazolium silanethiolates exhibit intense continua characteristic for systems containing highly polarizable protons. DFT and ab initio HF calculations confirm the transfer of proton and prove the cooperativity of hydrogen bonds in the studied systems.

Variable-temperature X-ray diffraction study of structural parameters of NH---S hydrogen bonds in triethylammonium and pyridinium silanethiolates

“…The presence of NHÁ Á ÁS hydrogen bonds (HB) is confirmed by the crystal structure data of -lactam antibiotics (Biswal & Wategaonkar, 2009) and active sites of many enzymes, e.g. cytochrome P-450, nitric oxide synthase, ironsulfur proteins (Biswal & Wategaonkar, 2009), cysteine proteases (Baranowska et al, 2012) or alcohol dehydrogenase (Dołęga et al, 2008(Dołęga et al, , 2009. Biologically active amines and other compounds with amino groups or imidazole rings may play the role of proton donors in these interactions.…”

“…For these reasons, special attention must be given to the construction of synthetic analogues to achieve an environment similar to that in protein (Parkin, 2004). With the use of tri-tert-butoxysilanethiol several analogues of cysteine proteases (Baranowska et al, 2012) and alcohol dehydrogenase (Dołęga et al, 2007(Dołęga et al, , 2008(Dołęga et al, , 2009Kropidłowska et al, 2007) were synthesized in our department. Tri-tert-butoxysilanethiol (TBST; Baranowska et al, 2012;Dołęga et al, 2007Dołęga et al, , 2008Dołęga et al, , 2009Kropidłowska et al, 2007) and lately tris-(2,6diisopropylphenoxy)silanethiol (TDST;Dołęga et al, 2012;Godlewska et al, 2014;Kazimierczuk et al, 2016), used in these models, possess large alkyl or alkylphenyl groups which form a hydrophobic coat surrounding the NHÁ Á ÁS hydrogen bonds (Dołęga et al, 2008).…”

“…TDST) results in the transfer of a proton from the thiol group to the N atom of a base and, as a consequence, the formation of a thiolate salt (e.g. Baranowska et al, 2006Baranowska et al, , 2012Kazimierczuk et al, 2016). In this work we have examined the products of reactions of the silanethiol (i) with an aliphatic compound of relatively high basicity (triethylamine) and (ii) with a heterocyclic aromatic base of moderate basicity (pyridine).…”

Charge-assisted N(+)–H···(−)S hydrogen bonds in the crystal structure of selected diammonium thiophenolates

“…Structural analyses indicate that the proton transfer from S-H to N across an SÁÁÁN bridge is facile as it was in the case of ammonium silanethiolates or thiolates and imidazolium silanethiolates [32].…”

The Syntheses and Crystal Structures of the First Disiloxane‐1,3‐dithiol and Its Cadmium Complex

“…However, silicon chalcogenides have been applied as reagents in organic syntheses, [30,31] and metal complexes with silyl chalcogenolate ligands have been used as precursors of metal chalcogenide nanoparticles. [36][37][38][39][40] Sulfur analogs of Si-O species include cyclosilthianes, [7,[41][42][43][44][45][46][47][48] silanethiols (characterized mainly as their metal salts), [8,15,16,[36][37][38][39][40][49][50][51][52][53][54][55][56][57][58][59][60] silanedithiols, [14,61,62] silyl sulfides, [63][64][65] di-and polysulf-ides, [66][67][68][69][70] and other rare species. [33]…”