Molecular Recognition of Imidazole Derivatives by Co(III)-Porphyrins in Phosphate Buffer (pH = 7.4) and Cetylpyridinium Chloride Containing Solutions

Abstract

Bymeans of spectrophotometric titration and NMR spectroscopy, the selective binding ability ofthe Co(III)-5,15-bis-(3-hydroxyphenyl)-10,20-bis-(4-sulfophenyl)porphyrin (Со(III)Р1) andCo(III)-5,15-bis-(2-hydroxyphenyl)-10,20-bis-(4-sulfophenyl)porphyrin (Со(III)Р2) towards imidazole derivatives of various nature (imidazole (L1), metronidazole (L2), and histamine (L3)) in phosphate buffer (pH 7.4) has been studied. It was found that in the case of L2, L3 the binding of the “first” ligand molecule by porphyrinatesCo(III)P1 and Co(III)P2 occurs with the formation of complexes with two binding sites (donor–acceptor bond at the center and hydrogen bond at the periphery of the macrocycle), while the “second” ligand molecule is added to the metalloporphyrin only due to the formation of the donor–acceptor bond at the macrocycle coordination center. The formation of stable complexes with two binding sites has been confirmed by density functional theory method (DFT) quantum chemical calculations and two-dimensional NMR experiments. It was shown that among the studied porphyrinates, Co(III)P2 is more selective towards to L1-L3 ligands, and localization of cobalt porphyrinates in cetylpyridinium chloride (CPC) micelles does not prevent the studied imidazole derivatives reversible binding. The obtained materials can be used to develop effective receptors for recognition, delivery, and prolonged release of drug compounds to the sites of their functioning. Considering that cetylpyridinium chloride is a widely used cationic biocide as a disinfectant, the designed materials may also prove to be effective antimicrobial agents.

Molecular Recognition of Imidazole-Based Drug Molecules by Cobalt(III)- and Zinc(II)-Coproporphyrins in Aqueous Media

“…In the Co(III)-5,15-bis-(4-sylfophenyl)-10,20-bis-(3-hydroxyphenyl)-porphyrin and Co(III)-5,15-bis-(4-sylfophenyl)-10,20-bis-(2-hydroxyphenyl)-porphyrin described by us in [ 14 ], the selectivity of binding imidazole derivatives is only observed when the first ligand is bound. When the second axial ligand is attached, the binding process is not selective.…”

“…For example, as [ 12 , 13 ] show, π–π interactions between the porphyrin receptor and the aromatic part of an amino acid significantly stabilize the Zn–porphyrin complex with tryptophan, in comparison with a similar complex with glycine (the stability constant of the complex increases from 60 L/mol in glycine to 1200 L/mol in tryptophan). In our previous work [ 14 ], we studied the recognition ability of two hydrophilic Co-tetraarylporphyrins with hydroxyl groups in the phenyl rings of the macrocycle towards imidazole and its derivatives (metronidazole and histidine) to find out whether additional hydrogen bonds could be formed between the hydroxyl groups of the receptor (porphyrinate) and the oxygen atoms of the nitro and carboxyl groups of the substrates. In the coproporphyrinates, the groups that are responsible for their selectivity in organic substrate binding are conformationally flexible propionic acid residues in four β-pyrrole positions of the macrocycle.…”

Macrocyclic Receptors for Identification and Selective Binding of Substrates of Different Nature

“…Molecular recognition is a process in which host molecules (receptors) select and bind guest molecules (substrates) into structurally highly organized systems through multipoint intermolecular interactions [ 1 , 2 , 3 , 4 , 5 , 6 , 7 ]. Porphyrins are extremely useful for this purpose.…”