Coordination Polymers of Cucurbit[n]urils with Metal Ions - Supramolecular Assemblies of Cucurbit[n]urils with Metal Ions - page 73

polymers with arrangements that are markedly different from those formed with-
out structure inducers. The most remarkable examples of formation of polydi-
mensional coordination polymers are seen in the coordination of Ln 3 + cations to
Q[6] or Q[7], which lead to the corresponding supramolecular assemblies in the
presence of transition metal dications (M trans 2 + ) in the HCl solution. The M trans 2 +
cations form [M trans Cl 4 ] 2 − anions and honeycomb-shaped cells via ion-dipole and
C-HCl interactions, and the tubular Q[ n = 6, 7]/Ln 3 + coordination polymers fill
the honeycomb cells [ 56 ].
Herein, we introduce a process beginning with tetrachloride transition metal
anions ([M trans Cl 4 ] 2 − , M trans = Cd, Zn, Cu, Co) as the “inducer” to undergoing
the “honeycomb” effect. These anions induce Sr 2 + cations to coordinate to Q[8]
molecules, resulting in the formation of 1D coordination polymers [ 56 ]. The X-ray
crystal structure given in Fig. 3.34 shows an overall view of the coordination fea-
tures and supramolecular assembly in the compound as a representative example
of all four Sr 2 + -Q[8]-[M trans Cl 4 ] 2 − systems. The [CdCl 4 ] 2 − anions appear to
form the honeycomb structure (Fig. 3.34 a), and two Sr 2 + cations coordinate to
the neighboring Q[8] molecules and form zigzag coordination polymers which
insert into the channels in the [CdCl 4 ] 2 − honeycomb framework. Each coordina-
tion polymer is surrounded by the [CdCl 4 ] 2 − anions (Fig. 3.34 b). Moreover, the
coordinated Q[8] molecules in the 1D coordination polymer are alternately sur-
rounded by six [CdCl 4 ] 2 − anions (Fig. 3.34 d). Part of the back of the inclined
Q[8] is close to the portal of the actinic Q[8] (Fig. 3.34 c). The distance of the
carbonyl oxygen from the carbonyl carbon (C = OC = O) in the inclined Q[8] is
about 3.0 Å, and the distance of the carbonyl oxygen from the methane carbon

Fig. 3.34 X-ray crystal structure of the compound from the Q[8]-Sr 2 + -[CdCl 4 ] 2 −

system: a
overall view of the coordination features and the supramolecular assembly and the [CdCl 4 ] 2 −

honeycomb-like frame; b a zigzag coordination polymer of Sr 2 +

cations to Q[8] molecules sur-

rounded by the [CdCl 4 ] 2 − anions; c details of coordination of Sr 2 +

cations to the portal carbonyl
oxygens of the Q[8] molecule; and d details of the interaction of [CdCl 4 ] 2 − with Q[8]