Inclusion compounds of cucurbit[8]uril with noble metal polyamine complexes

Abstract

Inclusion compounds of the macrocyclic cavitand cucurbit[8]uril (CB[8]) with the ruthenium(III) bis(ethylenediamine) complex {trans [Ru(en) 2 Cl 2 ]@CB[8]}Cl•27.5H 2 O (1), the gold(III) diethylenetriamine complex {[Au(dien)Cl]@CB[8]}Cl 2 •11H 2 O (2), and the gold(III) and platinum(II) cyclam complexes (H 3 O) 5 {[Au(cyclam)]@CB[8]}Cl 8 •18H 2 O (3) and {[Pt(cyclam)] 0.11 (H 2 cyclam) 0.89 @CB[8]}Cl 2 •16H 2 O (4), respectively, where cyclam is the tetra azamacrocyclic ligand, were synthesized. The inclusion compounds were synthesized both directly starting from CB[8] and the metal complexes with polyamines (en or dien) and by the two step method with the use of the cyclic polyamine ligand (cyclam) pre included into the cavity of the macrocycle. The inclusion compounds were characterized by X ray diffraction (1, 2, and 4), IR spectroscopy, electrospray ionization mass spectrometry, UV-Vis spectro scopy, and thermogravimetric analysis.Cucurbit[n]urils (C 6n H 6n N 4n O 2n , CB[n]; n = 5-10) comprise a family of macrocyclic molecules containing an open hydrophobic intramolecular cavity accessible through two hydrophilic portals formed by n carbonyl groups. 1-4 This structure determines the behavior of cucurbit[n]urils as cavitands, viz., host molecules capable of encapsulating guest molecules of suitable size into the inner cavity. A high negative electrostatic potential on the portals 3 is responsible for the formation of stable inclusion compounds of CB[n] with positively charged guests, for example, with alkylammonium cations. 2,3 The cavity sizes in cucurbit[n]urils with n > 6 are sufficient for the inclu sion of metal complexes with small organic ligands. The spectroscopic (NMR), calorimetric, and electrochemical studies showed that highly stable host-guest compounds are formed. 5-9 However, only a few inclusion com pounds of CB[n] with metal complexes were structurally characterized. 6,10-12 Complexes included into the bar rel shaped cavity of CB[n] can be fully embedded in the cavitand, as opposed to most of inclusion compounds of such receptors as calixarenes and cyclodextrins where com plexes are only partially encapsulated in the bowl shaped cavities. 13 In recent years, this class of compounds has attracted considerable interest because of the possibility of the inclusion of biologically active metal complexes into cavitands. This opens wide opportunities for the design of new generation prolonged action pharmaceuticals in which the host molecules prevents the guest molecules from rapid decomposition, decrease their toxicity, and have the transport function of the active component in the organism. 14 Recent studies 14-16 have shown that the in clusion of platinum polyamine complexes having antitu mor activity into cucurbit[n]urils leads to a substantial decrease in the toxicity of these complexes. Antitumor drugs containing inclusion compounds of CB[7] and CB [8] with platinum, palladium, and gold complexes were cov ered by patents. 17-20Previously, 21-25 we have shown that CB[8] forms inclusion compoun...

Formation of aqua and tetraammine Cu(II) complexes inside the cavities of cucurbit[6,8]urils: A DFT forecast

“…It is known that among CB[ n ] homologues the cavitand CB[7] is well‐soluble in water and as such it has been well studied. However, CB[8] and its higher homologues that have larger cavities are more often used in the synthesis of inclusion compounds with metal complexes, especially with polydentate ligands . It is for this reason that we chose CB[8] as one of the objects of this study.…”

“…These challenges can be addressed based on the use of quantum chemistry methods, which are a powerful tool that can provide detailed information on intricate molecular systems, as well as predict possible structures and properties of new compounds. Prior research has explored cucurbit[n]urils properties using both experimental and quantum‐chemical methods. So far, there have been relatively few publications devoted to quantum‐chemical studies of interactions between guest particles and cucurbiturils, in particular, those concerned with the modeling of the formation of the inclusion compounds .…”

Inclusion compounds of the copper(ii) and zinc(ii) complexes with cyclam in cucurbit[8]uril: synthesis and structure

“…[9][10][11][12][13] Interest in complexes with cyclam (1,4,8,11 tetraaza cyclotetradecane) and its derivatives is caused by their wide use in medicine, for instance, as antiviral drugs. 14- 16 To the present time, the inclusion compounds in CB [8] of the nickel(II), 17 iron(II), 18 palladium(II), 19 platinum(II), 20 and copper(II) 21 complexes with cyclam have been syn thesized and structurally characterized. In the structures of these compounds, the complex lies in the cavity of the cavitand molecule, while cyclam, except for the copper(II) complex, takes the most stable configuration trans III (of five theoretically possible trans configurations differed in the configuration of the nitrogen atoms ( Fig.…”