ISMSC 2007 - Università degli Studi di Pavia

PSB 5
Towards the development of new molecular nano-gates controlled via ionic
and optical inputs
Elena Aznar a , Rosa Casasús a , María Comes a , María Dolores Marcos a , Ramón Martínez-
Máñez a , Félix Sancenón a , Juan Soto a , Luis A. Villaescusa a , Pedro Amorós b , Joan Cano c , Eliseo
Ruiz c
a) Instituto de Química Molecular Aplicada (IQMA), Universidad Politécnica de Valencia,
Camino de Vera s/n, 46022, Valencia, Spain
b) Institut de Ciència dels Materials (ICMUV), Universitat de Vàlencia, 46071, Vàlencia, Spain.
c) Departament de Química Inorgànica, Universidad de Barcelona, E-08028 Barcelona, Spain.
Centre de Recerca en Química Teòrica (CERQT) and Institut de Nanociència i Nanotecnologia
(IN2UB), Universitat de Barcelona, Barcelona, Spain.
A nanoscopic gate may be defined as a molecular or supramolecular-based nano-device able to
control mass transport and that can be “opened” and “closed” at will by certain target ions,
molecules or other external stimuli. These systems with a molecular-and-material basis are
inspired in bio-channels and bio-gates and in general in biological processes that utilize
molecular movable mechanisms triggered by specific chemical species. Yet, the advanced
control via multiple chemical or physical inputs of motion-based functional processes such as
translocation, reversible mass movement, controlled molecular transport, etc. at nanometric
level is a landmark subject at the frontier of the knowledge for the upcoming design of
supramolecular sophisticated architectures. The development of such nanoscopic scaffoldings
could be achieved using pre-organised nanoscopic solid structures and supramolecular
functional units attached on the surface of the inorganic supports in a cooperative fashion. For
instance, recently reported examples have discovered that the anchoring of molecular entities
on 3D nanoscopic systems offers the opportunity to develop new supramolecular synergic
functional concepts that would be hardly achieved on “flat” surfaces (2D systems) or in
molecular-based systems. [1] This is especially so in the field of gated nanochemistry and its
relation with the design of nanoscopic supramolecular architectures incorporating chemical
entities which can act as a functional gate-like architectures and that allow to control the access
of (or from) a certain nanosite at will. The design of pores with stimuli-activated gating
mechanism is a potentially fertile research in the nano-chemistry and nano-biology fields. This is
a timely topic, yet the number of reported examples is still very low and usually of limited
applicability. We and other have recently reported the development of gate-like structures for
applications as controlled delivery systems or as new sensing paradigms. [2]
We report herein new designs of molecular gates on MCM41 mesoporous materials. Gate-1 is
driven by two different inputs in water; light and pH. It consists of switchable spirobenzopyrane
derivatives anchored in the pore outlets of a MCM41 support and negatively charged
dendrimers that acts as molecular stoppers. Gate-2 is both pH- and anion-driven and contains
simple anion binding sites (i.e. polyamines) anchored on mesoporous supports. Gate-3 consists
of a polyalcohol anchored on the pore outlets of a mesoporous structure and a nanoscopic tap
built up with gold nanoparticles functionalised with boronic acid derivatives. We also report
molecular modelling studies that have been carried out on the supramolecular Gate-2.
[1] A. B. Descalzo, R. Martínez-Máñez, F. Sancenón, K. Hoffman, K. Rurack, Angew. Chem.
Int. Ed., 2006, 45, 5924-5948.
[2] See for instance: R. Casasús, M. D. Marcos, R. Martínez-Máñez, J. V. Ros-Lis, J. Soto, L. A.
Villaescusa, P. Amorós, D. Beltrán, C. Guillem, J. Latorre, J. Am. Chem. Soc., 2004, 126, 8612-
8613. S. Giri, B. G. Trewyn, M. P. Stellmaker, V. S. –Y. Lin, Angew. Chem. Int. Ed., 2005, 44,
5038-5044.
Noble metal complexes with sulfur-containing calixarenes:
extraction, complexation and structure
Mashukov V.I. 1 , Kostin G.A. 1 , Torgov V.G. 1 , Korda T.M. 1 , Kalchenko V.I. 2
1 Institute of Inorganic Chemistry SB RAS, pr. Lavrent’eva, 3, Novosibirsk, Russia
2 Institute of Organic Chemistry NAS Ukraine, Murmanskaya str., 5, Kyiv, Ukraine
PSB 6
Functionalized calixarenes and thiacalixarenes are effective receptors for metal ions owing to
their -rich cavity and spatially oriented donor groups. Structure-property relationships have been
established for the complexation and extraction of Au, Pd, Ag and Pt chloride complexes by
calix[4,6]arenes-thioethers (1) and thiacalix[4]arenes-thioethers (2) modified by CH2-S-R groups
at the upper rim.
DPd DAu DAg
Size of macrocycle [n] in 1 [6] [4] [6] > [4] [4] [6]
bridging group (-S- or -CH2-) 2 > 1 1 > 2 2 > 1
substituents (R) in 1 Me > Bu >> p-Tol Bu> Me >> p-Tol Me > Bu >> p-Tol
The decrease in Au extraction (1 > 2) is due to the weakening of donor properties of the
upper-rim groups. Unusual influence of sulfur bridges (2 > 1) on Pd and Ag extraction can be
explained by additional interactions of metal ions with -aromatic system including S-bridges.
Slight recovery of Pd by unmodified thiacalix[4]arene-“cone” and the absence of extraction for
other conformations indirectly confirm the hypothesis of additional -bonding by the cavity.
The stoichiometry of extracted species and the constants of complex formation for (AuCl3)nL
(n=1-4), (PdCl2)nL (n=1-2) and AgClL have been determined. The equality of step-by-step
constants indicates that different sites of the calixarene coordinate metal ions independently
making the calixarenes very suitable platforms in the construction of polymetallic complexes.
Partition coefficients from 1-6 M HCl to diluents (toluene, CCl4, 1,2-dichloroethane) decrease
for all investigated calixarene-thioethers: DAu,DPd>>DAg>DPt. Compared with monodentate
analogues (R2S), the small increase in Au extraction ( 10) is determined by the structural
preorganization of receptor while the significant enhancement in Pd, Ag and Pt extraction (10 2 -
10 3 ) is related to both the structural preorganization and the helate effect. For Pd the
macrocyclic effect also leads to the acceleration of extraction by 2-3 orders of magnitude.
Moreover, the ditopic nature of 2 (hydrophobic upper rim and hydrophilic lower rim) promotes
additional acceleration (at the acidity of the aqueous phase > 3 M) owing to intramolecular
catalysis by protonated oxygen atoms in the alkoxy-groups.
The structures of (AuCl)4L and (PdCl2)2L
(L = 5,11,17,23-tetrakis-(butylthiomethyl) -
25, 26, 27, 28 -tetrapropoxycalix[4]arene)
have been determined by X-ray
crystallography. Monodentate coordination
of gold and helate coordination of palladium
to sulfur atoms of the donor groups have
been confirmed (see Figure). The crystal
lattice of (AuCl)4L consists of 2D-nets,
molecules being binded together by Au-Au
interactions (3,20-3,23 Å).
On basis of the investigation the parameters (calixarene structure, time of extraction, diluent,
CHCl) of effective combined or selective extraction of Pd and Au over other heavy metals have
been supposed.
The work has been partially supported by Joint SB-RAS-Ukrainian NAS project 4.12.