A new pyridine-based 12-membered macrocycle functionalised with different fluorescent subunits; coordination chemistry towards Cu^II, Zn^II, Cd^II, Hg^II, and Pb^II

Abstract

The coordination chemistry of the new pyridine-based, N2S2-donating 12-membered macrocycle 2,8-dithia-5-aza-2,6-pyridinophane (L1) towards Cu(II), Zn(II), Cd(II), Hg(II), and Pb(II) has been investigated both in aqueous solution and in the solid state. The protonation constants for L1 and stability constants with the aforementioned metal ions have been determined potentiometrically and compared with those of ligand L2, which contains a N-aminopropyl side arm. The measured values show that Hg(II) in water has the highest affinity for both ligands followed by Cu(II), Cd(II), Pb(II), and Zn(II). For each metal ion considered, 1:1 complexes with L1 have also been isolated in the solid state, those of Cu(II) and Zn(II) having also been characterised by X-ray crystallography. In both complexes L1 adopts a folded conformation and the coordination environments around the two metal centres are very similar: four positions of a distorted octahedral coordination sphere are occupied by the donor atoms of the macrocyclic ligand, and the two mutually cis-positions unoccupied by L1 accommodate monodentate NO3- ligands. The macrocycle L1 has then been functionalised with different fluorogenic subunits. In particular, the N-dansylamidopropyl (L3), N-(9-anthracenyl)methyl (L4), and N-(8-hydroxy-2-quinolinyl)methyl (L5) pendant arm derivatives of L1 have been synthesised and their optical response to the above mentioned metal ions investigated in MeCN/H2O (4:1 v/v) solutions.

Stability constants of complexes of Zn2+, Cd2+, and Hg2+ with organic ligands: QSPR consensus modeling and design of new metal binders

“…ions with 15 recent synthesized organic ligands. The predictions were performed for the comparison with 33 experimental log K values [5,6,[38][39][40][41][42] which were not presented in the sets used for the modeling. Mainly, the ligands are 12-and 15-membered macrocycles with the N, O and S donor atoms ( Table 3).…”

“…8 and 9 in Table 3). Figure 5 illustrates [5] d Reference [38] e Reference [39] f Reference [6] g Reference [40] h Reference [41] i Reference [42] ensemble modeling: the stability constant values were calculated as arithmetic mean of the predictions by means MLR and PRM CM. The predictions are characterized by reasonable values of R 0 2 = 0.800 and RMSE = 2.3.…”

“…For a construction of ligands with specific behavior (e.g., changing of luminescence at the complexation [4][5][6][7]), it is important to know ligand-binding properties to metal cations. The design of new metal binders represents an area of current interest in supramolecular chemistry [6].…”

Metal ion separation and protein removal from aqueous solutions using modified cellulose acetate membranes: Role of polymeric additives

“…The permeate flux of Cu(II) is lower than other metal ion solutions and the order of the permeate flux is Cd(II) > Co(II) > Zn(II) > Cu(II), which is in reverse trend of that observed in metal ion rejection studies. This is because of the fact that Cu(II) has higher affinity for N-donor ligands compared to Cd(II) and Zn(II) [30]. And hence, it is possible that Cu(II) can easily form more macromolecules than other metal ions chosen in this study.…”

Synthesis, coordination properties, and analytical applications of mixed donor macrocycles containing the 1,10-phenanthroline sub-unit

“…In between these two classes of compounds, many mixeddonor host macrocyclic chemical structures, also featuring rigid sub-units in the chelating ring, have been designed and synthesised for a variety of guest compounds, and successfully used for analytical purposes [1,2,4,[13][14][15][16][17][18][19][20][21][22]. In particular, π acceptor and redox-and photo-active 1,10-phenanthroline (phen) and 2,2'-bipyridine moieties have been either connected as side arms or incorporated into Schiff-base aza macrocycles, poly-aza macrocycles, crown ethers, cryptands and catenands as nonpendant integral part of the macrocyclic architecture, to give not only excellent multidentate structures capable of stabilising low-valent metal complexes and/or ligand-radical species, but also efficient sensing agents for ion-selective electrodes, fluorimetry, and selective ion transport across organic membranes [4,13,[23][24][25][26][27][28][29][30][31][32][33].…”