Electrospray ionization mass spectrometry of metal complexes. Gas phase formation of a binuclear copper(II)–5-Br-PADAP complex

• Published in: Analytica chimica acta 1999-05, Vol.390 (1), p.193-199
• Main Authors: Matsumoto, Atsushi, Fukumoto, Takao, Adachi, Hiroshi, Watarai, Hitoshi
• Format: Article
• Language: English
• Subjects: Binuclear complex; Chemistry; Copper(II)–pyridylazo complex; Electrospray ionization mass spectrometry; Exact sciences and technology; Mass spectrometry; Mass spectrometry/mass spectrometry; Nickel(II)–5-Br-PADAP complex; Organic chemistry; Reactivity and mechanisms
• ISSN: 0003-2670; 1873-4324
• DOI: 10.1016/S0003-2670(99)00222-6

The complexes formed from copper(II) and 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP or HL) in aqueous methanol solution was studied by electrospray ionization mass spectrometry. The solution of a 1:1 complex of Cu(II) with 5-Br-PADAP showed five peaks assignable to a binuclear complex [Cu 2L 2(AcO)] + and mononuclear complexes [CuL] +, [CuL(H 2O)] +, [CuL(AcOH)] + and [CuL(HL)] + (AcO=acetate). Collision activated dissociation revealed the relative order of bonding strengths; Cu–L>Cu–HL>CuL–AcOH>CuL–H 2O. The peak intensities of the binuclear complex showed second-order dependency on those of the mono complex. As for the solution of Ni(II)–5-Br-PADAP, no binuclear complex was observed in the mass spectra. Thus, it was suggested that [Cu 2L 2(AcO)] + was formed by the fast gas phase reaction: 2[CuL] ++AcO −⇄[Cu 2L 2(AcO)] +.