Tuning the Selectivity/Specificity of Fluorescent Metal Ion Sensors Based on N₂S₂ Pyridine-Containing Macrocyclic Ligands by Changing the Fluorogenic Subunit:  Spectrofluorimetric and Metal Ion Binding Studies

Abstract

Two new fluorescent chemosensors for metal ions have been synthesized and characterized, and their photophysical properties have been explored; they are the macrocycles 5-(2-quinolinylmethyl)-2,8-dithia-5-aza-2,6-pyridinophane (L5) and 5-(5-chloro-8-hydroxyquinolinylmethyl)-2,8-dithia-5-aza-2,6-pyridinophane (L6). Both systems have a pyridyl-thioether-containing 12-membered macrocycle as a binding site. The coordination properties of these two ligands toward CuII, ZnII, CdII, HgII, and PbII have been studied in MeCN/H2O (1:1 v/v) and MeCN solutions and in the solid state. The stoichiometry of the species formed at 25 degrees C have been determined from absorption, fluorescence, and potentiometric titrations. The complexes [CuL5](ClO4)(2).1/2MeCN, [ZnL5(H2O)](ClO4)2, [HgL5(MeCN)](ClO4)2, [PbL5(ClO4)2], [Cu3(5-Cl-8-HDQH-1)(L6H-1)2](ClO4)(3).7.5H2O (HDQ=hydroxyquinoline), and [Cu(L6)2](BF4)(2).2MeNO2 have also been characterized by X-ray crystallography. A specific CHEF-type response of L5 and L6 to the presence of ZnII and CdII, respectively, has been observed at about pH 7.0 in MeCN/H2O (1:1 v/v) solutions.

Role of Coordinated Water and Hydrogen‐Bonding Interactions in Stabilizing Monophenoxido‐Bridged Triangular CuIIMII­CuII Compounds (M = Cu, Co, Ni, or Fe) Derived from N,N′‐Ethylenebis(3‐meth­oxysalicylaldimine): Syntheses, Structures, and Magnetic Properties

“…[6][7][8] To the best of our knowledge, only three monophenoxido-bridged Cu II 3 compounds have been reported previously. [9,23] Clearly, compound 1 is an addition in the family of only a few monophenoxido-bridged Cu …”

“…[7,8] Relative to the diphenoxido-bridged systems, the extent of interaction in the monophenoxido-bridged compounds should be reduced because of the participation of one bridge in the latter case. [19] Of the three reported monophenoxido-bridged Cu II 3 compounds, [9,23] magnetic studies have been carried out for two. [9] In one of these cases, the interaction is weakly ferro-magnetic (J = +5.8 cm -1 ) despite the obtuse bridge angle of 113.3°.…”

Syntheses, Structures and Magnetic Properties of Trinuclear CuIIMIICuII (M = Cu, Ni, Co and Fe) and Tetranuclear [2×1+1×2] CuIIMnII–2CuII Complexes Derived from a Compartmental Ligand: The Schiff Base 3‐Methoxysalicylaldehyde Diamine Can also Stabilize a Cocrystal

“…[12,24] Of these three, the structure of (2); as already discussed, the bridging cores of both are twisted by an almost identical extent. [12] In 7, the two J values of -97.6 cm -1 and -89.5 cm -1 correspond to the bridge angles 129.84(13) and 121.10(12)°, respectively.…”

An efficient and selective flourescent optode membrane based on 7-[(5-chloro-8-hydroxy-7-quinolinyl)methyl]-5,6,7,8,9,10-hexahydro-2H-1,13,4,7,10-benzodioxatriazacyclopentadecine-3,11(4H,12H)-dione as a novel fluoroionophore for determination of cobalt(II) ions

“…doi:10.1016/j.aca.2008.09.051 fluorescence intensity in the presence the ion and/or a spectral change is required to ensure the sensitivity of sensing process [1,2]. Thus, in the case of such fluorescence sensors, the key point is the design of a fluorescence sensing element which usually consists of a fluorophore (signaling moiety) linked to an ionophore (recognition moiety), called as fluoroionophore [12,13]. The recognition process by fluoroionophores takes place by their ionophore part which is then converted to a change in the fluorophore's signal, brought about by the perturbation of such photoinduced processes as energy transfer, charge transfer, electron transfer, formation or disappearance of eximers and exciplexes [6,12,13].…”

“…Thus, in the case of such fluorescence sensors, the key point is the design of a fluorescence sensing element which usually consists of a fluorophore (signaling moiety) linked to an ionophore (recognition moiety), called as fluoroionophore [12,13]. The recognition process by fluoroionophores takes place by their ionophore part which is then converted to a change in the fluorophore's signal, brought about by the perturbation of such photoinduced processes as energy transfer, charge transfer, electron transfer, formation or disappearance of eximers and exciplexes [6,12,13]. In recent years, several fluorescence sensors have been developed for the detection of transition and heavy metal ions including Ag + [12], Ni 2+ [14], Cu 2+ [15,16], Pb 2+ [17,18], Cd 2+ [19], Hg 2+ [20,21] and Fe 3+ [22,23].…”