Unknown isopolyoxovanadate species detected by electrospray mass spectrometry

• Published in: Inorganica Chimica Acta Vol. 305; no. 2; pp. 118 - 126
• Main Authors: Walanda, Daud K, Burns, Robert C, Lawrance, Geoffrey A, von Nagy-Felsobuki, Ellak I
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 28-07-2000
• Subjects: Cluster complexes; Electrospray mass spectrometry; Polyoxovanadate complexes; Vanadium complexes; Cluster complexes; Electrospray mass spectrometry; Vanadium complexes; Polyoxovanadate complexes
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/S0020-1693(00)00122-5

Electrospray mass spectrometry (ES MS) has been used to identify many previously unknown isopolyvanadate anions and cations in aqueous solutions under non-equilibrium conditions. There is direct evidence that the evaporation process in ES MS has resulted in significant chemical effects, thereby generating many of these previously undetected species. As a consequence, ES MS offers insight into the polymerisation process. For the ammonium metavanadate system, negative-ion ES MS yielded two series, namely: [H
x
V
y
O
z
]
− (
x=0 to 1;
y=1 to 10;
z=3 to 26) and [H
x
V
y
O
z
]
2− (
x=0, 1;
y=3 to 17;
z=9 to 44). Also, the [H
2VO
4]
−, [V
10O
28]
6− and [H
5V
10O
28]
− anions were detected. In the positive-ion mode, three series of polyoxovanadate cations were observed, namely: [H
m+1
(VO
3)
m
]
+, [H
m−1
V
m
O
3
m−1
]
+ and [H
m−3
V
m
O
3
m−2
]
+. For the alkali metal metavanadate systems ions of the form [AV
m
O
3
m−2
]
− (
m=2, 4, 6; A=Li
+, Na
+ and K
+) were detected. In the positive-ion mode, at least two series of the form [A
m+1
(VO
3)
m
]
+ and [A
m+3
V
m
O
3
m+1
]
+ were observed. In all series, the protonated and unprotonated ions differed by {V
2O
5} mass units (characterised by ES MS as the formal building block in these clusters). At high cone-voltages, mixed-valence polyoxovanadate anions were observed for all the systems studied. On the other hand, for the positive-ion mode, the only mixed-valence polyoxovandates cations detected were for the potassium system.