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In the present study, we report three crystal structures of heterometallic Q[5]-based complexes. They are complexes of heterometallic cadmium and potassium ions/Q[5] capsules with a stoichiometry of {(CdCl)[K(H 2 O)][Cl@Q[5]]} + [CdCl 3 (H 2 O) 2 ] − 7H 2 O ( 1 ), heterometallic praseodymium and calcium/Q[5] pairs with a stoichiometry of 2{[Ca(H 2 O)(OH)]- μ -[Pr(H 2 O) 3 [Cl@Q[5]]]} 3+ 6Cl − 32H 2 O ( 2 ) and discrete heterometallic neodymium and potassium ions/Q[5] capsules with a stoichiometry of {[Nd(H 2 O) 3 ][(NO 3 )@Q[5]][K(H 2 O)][Nd(H 2 O) 3 (NO 3 ) 4 ]} 2+ 2(NO 3 ) − 8H 2 O ( 3 ).

Five crystals based on para-dicyclohexanocucurbit[6]uil (DCyHQ[6]) were synthesized and structurally characterized by single-crystal X-ray diffractions. They are {Dioxane@DCyHQ[6]}·18H2O (1), { [ Cu ( H 2 O ) 6 ] 2 DCyHQ [ 6 ] } 4 + · 2 SO 4 2 - · 10 H 2 O (2), { [ Zn ( H 2 O ) 6 ] 2 DCyHQ [ 6 ] } 4 + · 2 SO 4 2 - · 10 H 2 O (3), { [ Sr ( H 2 O ) 5 ] 2 DCyHQ [ 6 ] } 4 + · 5 Cl - · ( H 3 O ) + · 8 H 2 O (4), { [ Na ( H 2 O ) 4 ] 2 DCyHQ [ 6 ] } 2 + · 4 Br - · 2 ( H 3 O ) + · 14 H 2 O (5). The compound 1 which is a dioxane@DCyHQ[6] inclusion host–guest complex; the other three crystal structures of the compounds 2, 3 and 4 show supramolecular assemblies comprising of DCyHQ[6] and metal ions or their aqueous complexes through hydrogen bonding; while the crystal structure of the compound 5 shows a one-dimensional supramolecular polymer through direct coordination of sodium cations to the portal carbonyl oxygen atoms of the DCyHQ[6].

The crystal structure of {K[(H 2 O)@Q[5]][Zn(H 2 O) 3 Cl]} ZnCl 4 ·6(H 2 O) ( 1 ) is reported. It consists of an infinite 1D supramolecular chain constructed of heterometallic zinc and potassium ions/cucurbit[5]uril capsules held together through ion–dipole interactions and hydrogen bonding, and forms a novel hexagonal open framework.

Four host–guest complexes, {(gI)@(CyH) 6 Q[6]}·3H 2 O ( 1 ), {(gIIH 2 ) 2+ @(CyH) 2 Q[6]}·2Cl − ·21H 2 O ( 2 ), {(gIII)@Q[6]}·27H 2 O ( 3 ), and {(gIVH) + @(CyH) 2 Q[6]}·Cl − ·13H 2 O ( 4 ), have been prepared from cyclohexanocucurbit[6]uril, {(CyH) 6 Q[6]}, symmetrical dicyclohexanocucurbit[6]uril {(CyH) 2 Q[6]}, and cucurbit[6]uril {Q[6]} as hosts, and four different guests, namely 2-phenyl-2 H -imidazole (gI), the HCl salt of N 1 , N 4 -bis(pyridin-3-ylmethyl)butane-1,4-diamine (gII), benzylamine (gIII), and the HCl salt of 4-(1 H -imidazolyl)phenol (gIV). Their crystal structures have been characterized by single-crystal X-ray diffraction analyses and revealed that these hosts can form supramolecular assemblies through iondipole interactions, hydrogen bonding, CH···π or NH···π interactions, and π···π stacking.

Three host–guest complexes of methylsubstituted cucurbit[6]urils host and anthracene derivatives guests were synthesized and structurally characterized by single crystal X-ray diffractions and 1H NMR technique. The hosts are dodecamethylcucurbit[6]uril (DDMeQ[6]), α,α′,δ,δ′-tetramethylcucurbit[6]uril (TMeQ[6]), and hexa-methylsubstituted cucurbituril (HSMeQ[6]) made from 3a-methyl-glycoluril. The guests are 9,10-bis[N-(aminoethylene)aminomethyl]anthracene (AN1), 9,10-bis[N-(aminopropylene) aminomethyl]anthracene (AN2) and 9,10-bis[N-(aminobutylene)aminomethyl]anthracene (AN3). The crystal structures show the compounds 1–3 with stoichiometry of {DDMeQ[6]-AN1}2+2NO3−24H2O (1), {TMeQ[6]-AN2}2+4NO3− 2H3O+10H2O (2) and {2HSMeQ[6]-AN3}2+2Cl−25H2O (3) respectively, and the formation of an exclusion or inclusion host–guest complex is dependent on the length of the substituted alkyl chains on the anthracene.

Four molecular capsules based on three different cucurbit[5]urils, which are Dimethyl cucurbit[5]uril (DMeQ[5]), decamethylcucurbit[5]uril (Me 10 Q[5]) and the normal cucurbit[5]uril, were synthesized and structurally characterized by single-crystal X-ray diffractions. They are {[Gd 2 (H 2 O) 9 ][DMeQ[5]@Cl]} 5+ ·5Cl − ·13(H 2 O) ( 1 ), {[Nd 2 (H 2 O) 8 Cl][Me 10 Q[5]@Cl]} 4+ ·4Cl − ·9(H 2 O) ( 2 ), {K(H 2 O) 2 Cl·{[[Dy 2 (H 2 O) 6 Cl][Q [5]@Cl]} 2 } 8+ ·2{[Dy 2 (H 2 O) 7 Cl][Q[5]@Cl]} 4+ ·16Cl − ·44(H 2 O) ( 3 ) and 2{[Y 2 (H 2 O) 8 ][Me 10 Q[5]@Cl]} 5+ ·10Cl − ·48(H 2 O) ( 4 ). In the crystal structure of these compounds, molecular capsules included a Cl − anion and lidded with lanthanide cations were observed.

Four molecular capsules based on three methyl-substituted cucurbit[5]urils, which are α,β,δ-hexamethyl cucurbit[5]uril (α,β,δ-HMeQ[5]), decamethylcucurbit[5]uril (Me10Q[5]) and a pentamethylcucurbit[5]uril constructed of a monomethyl-glycouril (PMeQ[5]), were synthesized and structurally characterized by single crystal X-ray diffractions. They are {[α,β,δ-HMeQ[5]@Cl][Sr(H2O)2]2}3+3·Cl−·13(H2O) (1), {[α,β,δ-HMeQ[5]@(NO3)][Sr(NO3)(H2O)]2}+[NO3]−HNO3·4(H2O) (2), {[Me10Q[5]@(NO3)][Sr(NO3)(H2O)]2}+(NO3)−8(H2O) (3) and {[PMeQ[5]@Cl][Sr(H2O)2]2}3+3·Cl−·22(H2O) (4). In the crystal structure of these compounds, molecular capsules included a Cl− or a NO 3 - anion and lidded with strontium cations were observed.

Three new alkyl-substituted cucurbit[6]urils, symmetrical tetracyclopentano cucurbit[6]uril {TCyPQ[6]}, meta-tricyclopentano cucurbit[6]uril {m-TriCyPQ[6]} and meta-dicyclopentano cucurbit[6]uril {m-(CyP)2Q[6]}, were synthesized by using the controlled synthesis utilizing the readily available dimer of the unsubstituted glycouril, diether of cyclopentano glycoluril and the unsubstituted glycouril. These partial cyclopentano-substituted cucurbit[6]urils were characterized by single-crystal X-ray diffractions. In the crystal structure of compounds 2{TCyPQ[6]}·57H2O (1) and {m-TriCyPQ[6]}·23H2O (2), both of Q[6]s formed a molecular capsule included water molecules, and the capsules assembled one-dimensional supramolecular chains through the hydrogen bonding. In the crystal structure of compound 2{m-(CyP)2Q[6]}·(HV)2+·4Cl−·2(H3O)+·44H2O (3), a dumbbell shape host–guest inclusion complex N,N-dihexyl-4,4′-bipyridinium(HV2+) with m-(CyP)2Q[6] was formed, the m-(CyP)2Q[6] host selectively included the alkyl moiety of the guest through the hydrophobic cavity interaction and the ion-dipole interaction.

Three host–guest complexes, {(H2O)2@(CyH)2Q[6]} (4,4′-bpyH)+·Cl−·10H2O (1), {(1,4-dioxane)@m-TriCyHQ[6]}(4,4′-bpyH)+·Cl−·19H2O (2), {(4,4′-bpyH2)2+@TMeQ[6]}·2Br−·11H2O (3), were prepared with three different alkyl substituted cucurbit[6]urils, symmetrical dicyclohexanocucurbit[6]uril {(CyH)2Q[6]}, meta tricyclohexanocucurbit[6]uril (m-TriCyHQ[6]), symmetrical tetramethylcucurbit[6]uril (TMeQ[6]), and a HCl salt 4,4′-dipyridyl(4,4′-bpyHCl) or a HBr salt 4,4′-dipyridyl[4,4-bpy(HBr)2] guest. Their crystal structures characterized by single-crystal X-ray diffractions revealed that these hosts can form supramolecular assemblies with the halogen hydride salts of the guest 44bpy through the ion–dipole interaction, hydrogen bonding, C–H⋯π or N–H⋯π interaction and π⋯π stacking. The substituted alkyl group could affect the interaction model and assembled characteristic of the host and the guest.

Three supramolecular assemblies based on three new partial methyl-substituted cucurbit[5]urils, which are tetramethylcucurbit[5]uril (α,γ-TMeQ[5]), hexamethyl cucurbit[5]uril (α,β,δ-HMeQ[5]), Nonamethylcucurbit[5]uril (NMeQ[5]), were synthesized and structurally characterized by single-crystal X-ray diffractions. For the comparison with these new Q[5]s, crystal structure of an assembly constructing with normal Q[5] and K2PtCl6 was also reported. They are (α,γ-TMeQ[5])·15(H2O) (1), (α,β,δ-HMeQ[5])·2Cl−·2(H3O)+·7(H2O) (2), (NMeQ[5])·14(H2O) (3), ( Q [ 5 ] ) 2 · [ K ( H 2 O ) ] 2 + · [ PtCl 6 ] 2 - · 24 ( H 2 O ) (4). In the corresponding crystal structures, the molecular encapsulates included a water molecule and lidded water molecules at both of the portals were observed. Moreover, these molecular encapsulates are connected through hydrogen bonding and formed supramolecular chains or joined in pair.

Three supramolecular assemblies based on substituted cucurbit[6]uril: α,δ-tetramethylcucurbit[6]uril (TMeQ[6]) and α,γ,e-tricyclohexylcucurbit-[6]uril (m-TriCyHQ[6]), and α,γ,e-hexamethylcucurbit[6]uril (m-HMeQ[6]) with different metal ions were synthesized and structurally characterized by single-crystal X-ray diffractions. They are {TMeQ[6]@acetone[Ca(H2O)3]}2+·(CdCl4)2−10H2O (1), {[m-TriCyHQ[6]@dioxane][Na(H2O)2Cl]}15H2O (2) and {[m-HMeQ[6]]K2(H2O)4 Cl}Cl·15H2O (3). The crystal structures of these complexes showed the different interaction modes between these partial alkyl-substituted cucurbit[6]urils and the metal ions. In compound 1, a one-dimensional supramolecular chain of alternating TMeQ[6] molecules and [Ca(H2O)3]2+ complexes assembled through coordination bonding of the cation and the carbonyl oxygen of TMeQ[6]. The compound 2 was the first reported crystal structure of the m-TriCyHQ[6] with metal ion through the coordinate bonds, and the compound 3 was the first reported crystal structure of m-HMeQ[6]. It was unexpected that an ionic bonded chloride anion was at the portal of the two meta-substituted cucurbiturils.

Four supramolecular assemblies based on two partial substituted cucurbituril, α,δ-tetramethylcucurbit[6]uril (TMeQ[6]) and α,δ-dicyclohexanocucurbit[6]uril ((CyH)2Q[6]), with different metal ions were synthesized and structurally characterized by single-crystal X-ray diffractions. They are {[TMeQ[6]@2H2O]·[Zn(H2O)4]}·[ZnCl4]·12H2O (1), {[TMeQ[6]@H2O]·[Sr2Cl2]}·[Cl]2·10H2O (2), {TMeQ[6]·[CaCl]}·[Cl]·17.5H2O (3), {[(CyH)2Q[6]@acetone]·1.5[Ni(H2O)6]}·(NO3)32H2O (4). The crystal structures of these complexes showed that supramolecular chains were formed through different interaction modes. In complex 1, the transition metal ion Zn2+ was coordinated not only with water molecules but also directly with carbonyl oxygens of a portal of TMeQ[6]. The Zinc aqua complexes served as a bridge between TMeQ[6]s in the 1D supramolecular chains. In complex 2, each Sr2+ ion was coordinated directly with two carbonyl oxygen atoms at a portal of two TMeQ[6], and each TMeQ[6] was coordinated with four Sr2+ ions, resulting in the formation of supramolecular chains consisted of alternating metal ions and TMeQ[6]. In complex 3, two TMeQ[6] molecules were coordinated by two Ca2+ ions to form a assembled unit. The assembled units were connected through hydrogen bonds, leading to the formation of supramolecular chains. In complex 4, supramolecular chains consisted of alternating [Ni(H2O)]2+ complex cation and (CyH)2Q[6] were formed through hydrogen bonding.

Two partially methyl substituted cucurbituril, PMeQ[5] and HMeQ[6], were synthesized from 3a-methyl-glycoluril. They were characterized by 1 H NMR, ES-MS and single crystal X-ray diffraction. Ab initio calculations showed that each isolated methyl substituted cucurbit[ n ]uril is the most stable form among its all possbile isomers. One of the remarkable properties of these two partially substituted cucurbituril is their high solubility in the commonly used solvents such as water, methanol, and DMSO.

Three host–guest complexes, {acetone@m-TriCyHQ[6]}19H2O (1), {acetone@m-TriCyHQ[6]}{app}+Cl−12H2O (2), and {55dmbpy@m-TriCyHQ[6]}+ Cl−17H2O (3) were prepared with meta-tricyclohexyl cucurbit[6]uril (m-TriCyHQ[6]) and acetone, 3-amino-5-phenylpyrazole(app), and 5,5′-dimethyl-2,2′dipyridyl(55dmbpy), respectively. Their crystal structures along with that of {m-TriCyHQ[6]}22H2O (4) were characterized by single-crystal X-ray diffractions. The crystal structures of these host–guest complexes revealed that the host m-TriCyHQ[6] had a strong selectivity for different guest molecules, which were readily included in the cavity of m-TriCyHQ[6]. Small organic compounds, such as acetone and dioxane, showed a relatively strong tendency to interact only with the cavity of m-TriCyHQ[6]. However, guest 3-amino-5-phenylpyrazole hydrochloride preferred to interact with the portals of m-TriCyHQ[6] and guest 5,5′-dimethyl-2,2′-dipyridyl showed strong interactions with both the cavity and portals of m-TriCyHQ[6]. Basically, these guests form inclusion host–guest complexes with m-TriCyHQ[6], which were stabilized by the hydrophobic interactions in the cavity and the hydrophilic interactions at the portals.

The structures of five of the seven possible isomeric forms in the [Co(dien)(ampy)Cl]2+ system (three mer- and two fac-) have been determined by single crystal X-ray diffraction: (1) m1·Cl2·H2O, triclinic P1, a=7.3757(12), b=9.9250(16), c=11.5002(19) A, α=100.242(3)°, β=100.832(3)°, γ=94.615(3)°, Z=2; (2) m3·ZnCl4, monoclinic P21/c, a=11.057(3), b=9.581(2), c=17.568(4) A, β=95.560(5)°, Z=4; (3) m4·ZnCl4 monoclinic P21/n, a=8.4464(14), b=24.398(4), c=10.0645(17) A, β=112.510(3)°, Z=4; (4) f1·ZnCl4, triclinic P1, a=10.318(1), b=12.706(3), c=7.578(1) A, α=107.01(2)°, β=94.90(1)°, γ=99.07(1)°, Z=2; (5) f2·(ZnCl4)0.5·Cl·H2O, triclinic P1, a=7.7225(18), b=8.359(2), c=15.898(4) A, α=96.025(4)°, β=93.298(5)°, γ=116.191(4)°, Z=1. The last structure provides an example of spontaneous resolution. Two additional and independently determined structures are reported, in excellent agreement with these results. The structural work confirms the results of the detailed 2D NMR study. The agreement between the single crystal data and the calculated ab initio molecular parameters is excellent (within ±3%). The calculated total energies have been computed for the gas phase and aqueous solution, and are been used to explain the relative abundances of the seven isomers observed experimentally. The modes of isomer rearrangement are discussed.