Complexation and Extraction of PAHs to the Aqueous Phase with a Dinuclear Pt^II Diazapyrenium‐Based Metallacycle

Abstract

New palladium and platinum metallacycles have been synthesized by reaction between a 2,7-diazapyrenium-based ligand and Pd(II) and Pt(II) complexes. The inclusion complexes between the metallacycles and polycyclic aromatic hydrocarbons (PAHs) in CD(3)NO(2) and D(2)O were studied by NMR spectroscopy. The structures of the inclusion complexes of the Pt metallacycle as host with pyrene, phenanthrene, and triphenylene were confirmed by single crystal X-ray crystallography. The association constants between the Pt metallacycle and the selected PAHs were determined in CH(3)CN following the characteristic charge-transfer band displayed in their UV/Vis absorption spectrum. Although in aqueous solution all the complexes showed a 1:1 stoichiometry, in CH(3)CN the Job plot indicated a 2:1 stoichiometry for complexes with triphenylene and benzo[a]pyrene. The estimated association constants in water correlate with the hydrophobicity of the PAH, indicating that hydrophobic forces play an important role in the complexation process.

Recognition Properties and Self‐assembly of Planar [M(2‐pyridyl‐1,2,3‐triazole)2]2+ Metallo‐ligands

“…They have been exploited both in homo‐molecular systems and between electron rich and electron poor componentry. They have been used to promote molecular recognition, particularly between cationic electron‐poor hosts and neutral aromatic guests . Fujita, Yoshizawa and co‐workers have used organic guests such as pyrene to template the formation of multicavity structures, and Fujita and co‐workers have used the electronegativity difference between two guests to achieve heteromolecular guest binding within a single cavity .…”

Dimensional Matching of Polycyclic Aromatics with Rectangular Metallacycles: Insertion Modes Determined by [CH⋅⋅⋅π] Interactions

“…Despite this fact, their use as molecular receptors is undoubtedly underdeveloped. [12] Considering our previous work on the complexation of polycyclic aromatic hydrocarbons (PAHs) in aqueous media with Pd II /Pt II dinuclear metallacycles, [13] we envisaged the possibility of extending our library of receptors by varying their sizes. In this manner, a dimensional matching between the designed hosts and polycyclic aromatics could be anticipated, leading, eventually, to rational control over the insertion modes of the guests.…”

Rationally Designed Supramolecular Organic Hosts for Benzo[a]pyrene Binding and Detection

“…The fluorescence emission of benzo[a]pyrene (11) and of BODIPY 12 were integrated with respect to wave number, and the efficiency of energy transfer was determined by measuring the percentage of BODIPY emission from analyte excitation compared to direct excitation [Equation (1)]. 200 μL of the macrocycle host, 20 μL of the PAH analyte, and 20 μL of the BODIPY 12 fluorophore were added to 2.5 mL of PBS.…”

“…These host-guest complexes are governed by a variety of noncovalent interactions such as π-π stacking, [3] electrostatic interactions, [4] van der Waals forces, [5] and hydrophobic binding. [6] Supramolecular hosts, including cyclodextrins, [7] calix[n]arenes, [8] Exbox, [9] cucurbiturils, [10] and metallomacrocycles [11] have been used in a variety of applications, including the extraction and detection of highly toxic polycyclic aromatic hydrocarbons (PAHs). [12] Despite the long history of supramolecular chemistry in general, and synthetic macrocycles in particular, little research has been done towards developing rational structure-property relationships between subtle structural variations in the supramolecular hosts and the ability of these hosts to engage in the requisite intermolecular interactions.…”

“…Schematic illustration of energy transfer from benzo[a]pyrene(11) to BODIPY fluorophore 12. This energy transfer is more efficient in the presence of certain organic aromatic macrocycles.…”