Self‐Assembled Tetragonal Prismatic Molecular Cage Highly Selective for Anionic π Guests

Abstract

The metal-directed supramolecular synthetic approach has paved the way for the development of functional nanosized molecules. In this work, we report the preparation of the new nanocapsule 3-(CF3SO3)8 with a A4B2 tetragonal prismatic geometry, where A corresponds to the dipalladium hexaazamacrocyclic complex Pd-1, and B corresponds to the tetraanionic form of palladium 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (2). The large void space of the inner cavity and the supramolecular affinity for guest molecules towards porphyrin-based hosts converts this nanoscale molecular 3D structure into a good candidate for host–guest chemistry. The interaction between this nanocage and different guest molecules has been studied by means of NMR, UV/Vis, ESI-MS, and DOSY experiments, from which highly selective molecular recognition has been found for anionic, planar-shaped π guests with association constants (Ka) higher than 109 m−1, in front of non-interacting aromatic neutral or cationic substrates. DFT theoretical calculations provided insights to further understand this strong interaction. Nanocage 3⋅(CF3SO3)8 can not only strongly host one single molecule of M(dithiolene)2 complexes (M=Au, Pt, Pd, and Ni), but also can finely tune their optical and redox properties. The very simple synthesis of both the supramolecular cage and the building blocks represents a step forward for the development of polyfunctional supramolecular nanovessels, which offer multiple applications as sensors or nanoreactorsWe are grateful for financial support from the MICINN of Spain (CTQ2009-08464/BQU to M. C., CTQ2011-25086/BQU, CTQ2011-23156/BQU, PhD grant AP2010-2517 to M. G. B, INNPLANTA- INP-2011-0059PCT-420000-ACT1 and Consolider-Ingenio CSD2010-00065), the FEDER fund (European Fund for Regional Development) for the grant UNGI08-4E-003, the European Research Council for Project ERC-2011StG-277801 to X. R. and ERC-2008-StG-29910 to M. C., and the Generalitat de Catalunya (2009SGR637, 2009SGR528, and a Ph.D. grant to C. G. S.). X. R. and M. C. thank ICREA-Academia awards. I. I. thanks MINECO for a Ramon y Cajal contract. We thank Dr. Teodor Parella for fruitful discussions. We thank STR's from UdG for technical support, and we also acknowledge the computer resources, technical expertise, and assistance provided by the Barcelona Supercomputing Center Centro Nacional de Supercomputacion, and Centre de Serveis Cientifics i Academics de Catalunya (CESCA) for partial funding of computer tim

Sponge-like molecular cage for purification of fullerenes

“…4 Á (X) 8 differs from the recently described cage 3 Á (X 0 ) 8 (X 0 ¼ ClO 4 , CF 3 SO 3 ) (ref. 51) in the aromatic part of the hexaaza macrocyclic ligands; 3 Á (X 0 ) 8 contained 1,4-substituted benzene rings that have been replaced by biphenyl rings in 1b. As a result, the distance between metalloporphyrins is enlarged from 7.5 Å in 3 Á (X 0 ) 8 to 14.1 Å in 4 Á (X) 8 …”

“…The dimensions of 4 8 þ derived from DOSY NMR are, as expected, larger than in tetragonal cage 3 8 þ (ref. 51).…”

Phenylene‐Bridged Core‐Modified Planar Aromatic Octaphyrin: Aromaticity, Photophysical and Anion Receptor Properties

“…Thus, protonation of the basic imino nitrogen atoms by using HClO 4 led to the formation of atetraprotonated species, which created ad riving force to attract anions towardsi ts cavity. [5] As the concentration of the acidi ncreased, the band at 619 nm gradually becamel ess intense and an ew band appeared at 655 nm, with ab athochromic shift of 36 nm, which suggested the formationo faprotonated species. Thus, the anion-binding experiments were performed with an excess of HClO 4 acid ( 10 À2 m).…”

“…Theird iversep roperties have been attributed to significant p-electronc onjugation, larger cavity sizes, aromatic characteristics, and the ability of expandedp orphyrins to adopt ar ange of conformations. [1][2][3][4][5][6] The conformations that they exhibit dependso nt he number of conjugated pyrrole and heterocyclic rings, the number of meso linkages, the nature of the heteroatom, and the substituents presento nt he meso carbon atoms. For example, the [34 p]o ctaphyrins( 1) adopt a" figure-eight" conformation in the solid state and, hence,l ose the aromaticity of the macrocycle.…”

Using Complementary Ligand Denticity to Direct Metallosupramolecular Structure about Metal Ions with Square‐Planar Geometry

“…Other tridentate chelators than terpy have also been used, for example by Ribas and coworkers (Figure ). They utilised a macrocyclic ligand with two tridentate diethylene triamine sites, with biphenylene linkers ( L26 , they also used a smaller macrocyclic ligand in a comparable synthesis) to form a [Pd 2 L26 (AcO) 2 ] 2+ clip. This was combined in 4 : 2 ratio with a tetra ‐caboxylate Zn II porpyrin ligand ( L27 ), resulting in the formation of a [Pd 8 Zn 2 L26 4 L27 2 ] 8+ cage (Figure18) .…”