An Enolisable Barbiturate with Adjustable Hydrogen‐Bonding Structure for UV/Vis Detection of Nucleic Acid Bases and Related Compounds

Abstract

The use of hydrogen-bonding patterns in the same way as is known from DNA building blocks is a challenge for the construction of novel types of suitable chromophoric probes. This feature has been utilised for the construction of a novel type of UV/Vis probe for detection of supramolecular AAD or DAD sequences (A=hydrogen bond acceptor, D=hydrogen bond donor). Here we report on the structure of the enolisable chromophore 1-n-butyl-5-(4-nitrophenyl)barbituric acid (1), which has an adjustable hydrogen-bonding pattern. The position of the keto-enol equilibrium of this dye is strongly influenced both by the solvent polarity and by the chemical environment. Furthermore, the recognition properties of the barbiturate were examined by the use of seven artificial receptors: the pyridine bases 2,6-diaminopyridine (DAP), 2,6-diacetamidopyridine (DAC) and 2,6-bis(trifluoroacetamido)pyridine (TFA), as well as the nucleic acid bases 9-ethyladenine (EtAd), 9-ethylguanine (EtGu), 1-n-butylcytosine (BuCy) and 1-n-butylthymine (BuTy). It was found that 1 can interact with these bases either through acid-base interaction or by hydrogen-bonding complexation. The balance between the interactions is dependent both on the basicity strength and on the presence of a suitable recognition sequence in the base. The induced formation of the enol form of 1 thus causes a significant UV/Vis shift as function of the nature of the base.

NMR and quantum chemical studies on association of 2,6-bis(acylamino)pyridines with selected imides and 2,2′-dipyridylamine

“…On the other hand, stronger hydrogen bonding capability of proton in the NHCOCF 3 group (as compared to that in NHCOCH 3 ) is expected to strengthen the complex stability. 2,6-Bis(trifluoromethylcarbonylamino)pyridine has been investigated as a hydrogen bonding counterpart stabilizing the flavin radical anion [48] and as a hydrogen bonding receptor for barbiturate [49]. The acylation of amino moiety, however, not always led to the greater stability of non-covalent associates [33].…”

Tuning the hydrogen-bonding strength in 2,6-bis(cycloalkylcarbonylamino)pyridine assemblies by variable flexibility. Association constants measured by hydrogen-bonded vs. non-hydrogen-bonded protons

“…Thus monitoring several nuclei is the method of choice to improve the reliability of obtained results. Triple hydrogen-bonded associates are met in many structures as in DNA [14,15], amides [16,17], artificial sensors [18][19][20][21][22], materials [23], non-covalent polymers [4,[24][25][26][27][28] and in recently observed associates of orotic acid [29,30]. Triple hydrogen-bonded assemblies carrying 2,6-diaminopyridine DAD-hydrogen bonding moiety were studied by some groups with the use of various methods [4,6,[31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] and also by us [48,49].…”

Interactions of Enolizable Barbiturate Dyes

“…Related studies were done with the enolizable chromophore 1‐ n ‐butyl‐5‐(4‐nitrophenyl)barbituric acid (NPBA), which showed the complexity of this field . Unfortunately, the optically measured effects by UV/Vis spectroscopy, which are caused by supramolecular complex formation of NPBA, were not very significant.…”

“…Those compounds 4 are accessible by nucleophilic aromatic substitution of 2,4‐dinitrofluoro‐benzene with barbituric acid salts . The mono N‐ alkyl substituted BA 4 b is beneficial to obtain a better solubility in nonpolar solvents . Additionally, the n ‐butyl group barricades one hydrogen‐bonding sequence of the BA, thus solely a 1:1‐complex formation can take place ,…”

“…Brønsted acid strength of the dyes has been measured by common acid–base titration and the results have been evaluated by means of the established Henderson–Hasselbalch equation (HHE) according to our previous study …”