A Porphyrin Coordination Cage Assembled from Four Silver(I) Triazolyl‐Pyridine Complexes

Abstract

The synthesis of a zinc(II) porphyrin 1 with four appended triazolyl-pyridine chelates is reported. Complexation of the porphyrin peripheral ligands with Ag(I) ions in a 1:2 binding stoichiometry afforded quantitatively the coordination cage [Ag4 (1)2 ](4+) . The assembly and disassembly processes of the cage were investigated in solution using UV/Vis spectroscopy. The mathematical analysis of the data obtained in the UV/Vis titration of 1 with Ag(I) confirmed the assembly in CH2 Cl2 /MeOH (90:10) solution of a species having a 1:2 porphyrin/silver stoichiometry and assigned to it an overall stability constant of 5.0×10(26) M(-5) . The use of a model system allowed an independent assessment of a microscopic binding constant value (Km ) for the interaction between the triazolyl-pyridine ligand and Ag(I) . The coincidence that existed between the Km values extracted from the model system and the titration of 1 provided an indication of the quality and fit of the data analysis. It also allowed the calculation of the average effective molarity (EM) value for the three intramolecular processes that led to the cage assembly as 2.6 mM. Simulated speciation profiles supported the conclusion that at millimolar concentration and working under strict stoichiometric control of the silver/porphyrin ratio, the cage [Ag4 (1)2 ](4+) was the species exclusively assembled in solution. On the other hand, when the concentration of added Ag(I) was approximately 2.6 mM, 50 % of the coordination cage disassembled into open aggregates.

Positive Allosteric Control of Guests Encapsulation by Metal Binding to Covalent Porphyrin Cages

“…Our previous work has focused on the synthesis of coordination and covalent architectures incorporating metalloporphyrins . In particular, flexible covalent cages incorporating orthogonal binding sites, metalloporphyrins and 1,2,3‐triazoles, were obtained using a DABCO‐templated copper(I)‐catalyzed alkyne‐azide reaction (DABCO=1,4‐diazabicyclo[2.2.2]octane).…”

“…Especially,s tructures incorporatingm etalloporphyrins with ad efined binding pocket have shown molecular recognition properties andc atalytic activity. [11,[59][60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75] Our previous work has focused on the synthesis of coordination [76] andc ovalent architectures incorporating metalloporphyrins. [77][78][79] In particular,f lexible covalent cages incorporating orthogonal binding sites, metalloporphyrins and 1,2,3-triazoles, were obtained using aD ABCO-templated copper(I)-catalyzed alkyne-azider eaction (DABCO = 1,4-diazabicyclo[2.2.2]octane).…”

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

“…Up-field shift of the Co(III)P(1-2) complexes proton signals agreed well with the DOSY experiments. The experiments were used for the compounds identification according to their self-diffusion coefficients, which depend on the size and the form of a molecule in accordance with the Stokes–Einstein equation [ 32 , 33 , 34 , 35 ]. The complexes Co(III)P(1-2) are characterized by a higher relative value of the self-diffusion coefficient to the solvent (0.39), than the complexes with ligands (0.34 and 0.28), which confirms the changes of molecular mass as a result of the complex formation.…”

“…The complexes Co(III)P(1-2) are characterized by a higher relative value of the self-diffusion coefficient to the solvent (0.39), than the complexes with ligands (0.34 and 0.28), which confirms the changes of molecular mass as a result of the complex formation. In addition to this, Co(III)P2 and Co(III)P2-L2, and Co(III)P2-L3 complexes were completely characterized by means of two-dimensional correlation spectroscopy (1H–1H 2D of COSY), which also is applied for the determination of macromolecules chemical structure [ 17 , 30 , 31 , 32 , 33 , 34 , 35 ].…”

Accuracy of Determination of Self-Diffusion Coefficients in Studies of Porphyrin-Based Complexes by 2D DOSY

“…[12][13][14][15] Modern NMR methods play a special role in studied of formation of intermolecular complexes and associates, [16][17][18] and in identifying supramolecular assemblies. [19][20][21][22][23][24] In studies of intermolecular interactions in porphyrin complexes, a number of efficient approaches can be applied, including classical analysis of chemical shifts and relaxation times and modern two-dimensional methods such as nuclear Overhauser effect [25][26][27] and diffusion-ordered spectroscopy (DOSY).…”