The crystal structure of the heteroditopic cryptand (L) formed by
Schiff-base condensation of tris(2-aminoethyl)amine and
2,2′,2″-nitrilotris(ethyleneoxy)tris(benzaldehyde)
followed by reduction with NaBH
4
has been determined. The
molecule has an endo-endo conformation with a
pseudo-three-fold symmetry axis passing through the two bridgehead
nitrogens. This symmetry is maintained in chloroform solution as
indicated by its
1
H NMR spectrum. The cryptand accepts a
metal ion (Cu
II
, Zn
II
or Ni
II
) inside
the cavity forming mononuclear cryptates of general formula
[ML][ClO
4
]
2
. The metal ion occupies the
N
4
end of the cavity. The light blue CuN
4
chromophore thus formed exhibits an axial EPR spectrum with very small
A
∥
value
(63 × 10
-4
cm
-1
)
and a low-energy ligand-field band. Nickel(II) initially
forms a blue [NiL][ClO
4
]
2
complex which on
dissolving in moist MeCN solution crystallizes as purple rectangular
parallelopipeds with the formulation
[NiL(H
2
O)(MeCN)][ClO
4
]
2
·H
2
O·2MeCN. The crystal structure of this complex has also
been determined. The Ni
II
ion is octahedrally co-ordinated
with the equatorial sites occupied by the three secondary amino N atoms
of the cryptand and the N atom of the bound MeCN. The axial sites are
occupied by the bridgehead N and the O atom of the water molecule which
enters the cavity forming a cascade complex.
通过Schiff-base缩合反应形成的异双齿
穴醚(L)的晶体结构,由
三(2-氨基乙基)胺和2,2′,2″-氮三(
乙烯氧基)三(
苯甲醛)组成,随后用NaBH4还原,已被确定。该分子具有endo-endo构型,通过两个桥头氮原子存在一个伪三重对称轴。这种对称性在
氯仿溶液中得到保持,如1H NMR谱所示。该
穴醚在腔内接受
金属离子(Cu II、Zn II或Ni II),形成通式为[ML][ClO4]2的单核穴合物。
金属离子占据腔内N4端。形成的CuN4光
蓝色素表现出轴向EPR谱,具有非常小的A∥值(63 × 10-4 cm-1)和低能量
配体场带。
镍(II)最初形成蓝色的[NiL][ClO4]2配合物,在湿润的MeCN溶液中溶解后结晶为紫色矩形平行六面体,具有配方[NiL(
H2O)(MeCN)][ClO4]2· ·2MeCN。该配合物的晶体结构也已被确定。Ni II离子是八面体配位的,赤道位点由
穴醚的三个二级
氨基N原子和结合的MeCN的N原子占据。轴向位点由桥头N和进入腔内的
水分子形成瀑布型配合物的O原子占据。