title: 9, 10-Bis(8-Quinolinoxymethyl)Anthracene--A Fluorescent Sensor for Nanomolar Detection of Cu(2+) with Unusual Acid Stability of Cu(2+)-Complex.
abstract: In this work, the dipod 9,10-bis(8-quinolinoxymethyl)anthracene (1) and for comparison, monopod 9-(8-quinolinoxymethyl)anthracene (2) have been synthesized. The fluoroionophore 1 in pH 7.1 HEPES buffered CH3CN:H2O (4:1 v/v) solution shows quenching only with Cu(2+) with lowest limit of detection 150 nM, amongst various metal ions. Fluoroionophore 1 could also be applied to sense Co(2+) with lowest limit of detection 600 nM. By modulating the pH of the solution and concentration of Cu(2+), 1 shows respective "On-Off-On" and "On-Off" fluorescent switching. The self-assembly of two Cu(2+) ions and two molecules of fluoroionophore 1 to form closed structure [Cu2(L)2](4+) seems to be responsible for nanomolar sensitivity towards Cu(2+). The combination of delayed second protonation of 1 (pK(a2) = 2.6) and stepwise protonation of [Cu2 L2](4+) causes unusual stability of [Cu(LH)2](4+) even at pH < 2.
authors.affiliation: Department of Chemistry, UGC Centre for Advanced Studies, Guru Nanak Dev University, Amritsar, 143005, India. prabhpreet.chem@gndu.ac.in.
authors.forename: Prabhpreet
authors.initials: P
authors.lastname: Singh
authors.affiliation: Department of Chemistry, UGC Centre for Advanced Studies, Guru Nanak Dev University, Amritsar, 143005, India.
authors.forename: Rahul
authors.initials: R
authors.lastname: Kumar
authors.affiliation: Department of Chemistry, UGC Centre for Advanced Studies, Guru Nanak Dev University, Amritsar, 143005, India. subodh_gndu@yahoo.co.in.
authors.forename: Subodh
authors.initials: S
authors.lastname: Kumar
mesh_terms: D000143:Acids / Q000737:chemistry*; D000873:Anthracenes / Q000737:chemistry*; D066241:Carbon-13 Magnetic Resonance Spectroscopy; D003300:Copper / Q000032:analysis*; D005456:Fluorescent Dyes / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D057230:Limit of Detection; D066244:Proton Magnetic Resonance Spectroscopy
chemical_list: D000143:Acids; D000873:Anthracenes; D005456:Fluorescent Dyes; D003300:Copper
keywords: 8-hydroxyquinoline; Chemosensor; Co2+; Cu2+; Fluorescence quenching; pH stability