Chemistry Reference
In-Depth Information
Fig. 9 Fractional total ion current measured via ESI-MS as a function of the ligand to AuClPPh
3
ratio, [L
6
]/[PPh
3
]. Triphenylphosphine ligands are increasingly replaced on the metal complexes as
L
6
is added incrementally to a solution comprising 10.0 mg of AuClPPh
3
dissolved in chloroform/
methanol (50:50). The symbols are assigned as follows:
red circles
, [Au(PPh
3
)
2
]
+
;
blue diamonds
,
[Au
2
L
6
2
]
+
;
green wedges
, [Au
2
L
6
2
Cl]
+
; and
black triangles
, [Au
2
L
6
3
Cl]
+
. The
insert
displays the
fractional total ion current for 0
[L
6
]/[PPh
3
]
3. Figure reproduced from [
142
]
observed via ESI-MS could be 'tuned' by the nature of the gold-ligand complex
distribution prior to reduction. Figure
10
summarises the fractional product distri-
bution of AuNPs as a function of [L
6
]/[PPh
3
] and will be discussed in greater detail
in Sect.
2.4.3
.
2.4.2 Reduction Phase
In 2006 Wang et al. [
149
] used ESI-MS and UV-Vis spectroscopy to monitor the
formation of AuNCs upon the slow reduction of AuClPPh
3
in chloroform by the
addition of 5 equiv. of BTBC. A range of PPh
3
-protected AuNC intermediates were
observed by examining aliquots of the reaction at various time intervals. Their
studies were extended to the reduction of AuClPPh
3
in chloroform mixed with
equimolar bisphosphine ligand Ph
2
P-(CH
2
)
n
-PPh
2
,
3-6. It was concluded that
the bidentate ligands showed exceptional size selectivity, Fig.
11
, compared to
the monodentate triphenylphosphine ligand. Monodisperse [Au
11
(L
n
)
5
]
3+
was
selectively synthesised when
n
¼
3.
The formation of gold nanoclusters described initially by Wang et al. was later
refined by Hudgens et al. [
140
],
¼
in which bisphosphine (L
3
)-protected gold
