Mimicking [2,2]Paracyclophane Topology: Molecular Clips for the Coordination-Driven Cofacial Assembly of π-Conjugated Systems

Abstract

Self-assembly of CuI dimers, featuring a bridging phosphole ligand, and ditopic cyano-substituted chromophores affords nanosize supramolecular cationic rectangles. Due to the short Cu-Cu distance in the bimetallic clips, the coordinated chromophores are forced to participate in cofacial pi-pi interactions as evidenced by X-ray data. In addition, intermolecular pi-pi interactions in the solid state are observed leading to infinite columns of pi-stacked (para-phenylenevinylene)-based chromophores.

The Synthesis, Photophysical Characterization, and X‐Ray Structure Analysis of Two Polymorphs of 4,4′‐Diacetylstilbene

“…The colorless polymorph of 1 adopted (E)-geometry about the C¼C bond, with a C(1 i )ÀC(1)ÀC(2) bond angle of 125.7(2)8 (symmetry code i for the colorless polymorph is defined as À x, 1 À y, À z). The observed C¼C bond length of 1.338(4) as well as other bond lengths and angles in 1 correlated with the values for a similar stilbene derivative [16]. The only difference (2) 1.4622(11) C(5)ÀC (8) 1.489(3) N(1)ÀN (2) 1.3361(10) C(4)ÀC (5) 1.394(3) N(2)ÀN (3) 1.2766(10) C(1)ÀC (2) 1.467(3) N(3)ÀC (5) 1.4206(11) C(1)ÀC(1 i ) 1.338(4) C(5)ÀC (6) 1.3970(12) C(8)ÀC (11) 1.4905(12) O(2)ÀC (11) 1.2271(11) C(11)ÀC (12) 1.5076(12) C(1)ÀO(1)ÀC (4) 109.78(7) C(1 i )ÀC(1)ÀC (2) 125.7(2) O(1)ÀC(1)ÀC (2) 110.69 (7) C (5)ÀC (8)ÀC (9) 119.31(16) N(3)ÀN (2)ÀN(1) 114.08 (7) O(1)ÀC (8)ÀC (9) 120.18(18) N(2)ÀN(30ÀC (5) 112.33 (7) C (3)ÀC (4)ÀC (5) 120.43(16) C(6)ÀC(5)ÀC (10) 119.65(8) O(2)ÀC(11)ÀC (12) 121.01 (8) a ) Symmetry code i is defined as À x, 1 À y, À z. between individual molecules of 1 was that the yellow polymorph deviated from planarity more than individual molecules of 1 in the colorless polymorph.…”

Can Coordination‐Driven Supramolecular Self‐Assembly Reactions Be Conducted from Fully Aliphatic Linkers?

“…In addition, all the metric parameters of the dicationic (Cu I )2(B)2 cores of the derivatives 10-18 are very similar to those of the molecular clip A [7] and the metallacycles C-D (Table S4). [10][11][12] Finally, no specific intra-or inter-molecular short contact interactions involving the ligands B are observed. All this allows to preclude sterical congestion effects at the (Cu I )2(B) fragments to justify the differences in the molecular architectures of the derivatives 10-18.…”

“…These results prompted us to explore the reaction of a family of linear ditopic FA cyano-capped linkers 1-9 NC-(CH2)x-CN (x = 3-10,12) with the pre-assembled bimetallic Cu(I) U-shape molecular clip A [7] (Scheme 1b), stabilized by the hemilabile 2,5-bis(2-pyridyl)phosphole ligand B and bearing short intermetallic distances (d(Cu-Cu) = 2.55 Å). [8] Derivative A was previously identified as a versatile and strongly convergent 'U-shape' molecular clip for the CDS syntheses of a large series of compact metallacycles C [9] upon its reaction with various ditopic cyano-capped π-conjugated linkers [10] or with the metal-based linear linker [Au(CN)2] -(Scheme 1a). [11] Within the resulting assemblies, specific inter-linkers interactions (π-π or aurophilic intra-and intermolecular interactions) were observed, playing presumably a key role in the selective formation of these compact metallacycles, which was recently supported by the reaction of A with a series of cyano-capped ditopic linkers carrying both 'rigid' π-conjugated systems and 'flexible' linear [a] Dr Accepted Manuscript Figure 1.…”

“…The solid state molecular structures of all the derivatives 10-18 were established by X-ray diffraction studies [8,13] performed on single crystals obtained at RT from pentane diffusion into CH2Cl2 crude solutions. In all the supramolecular structures 10-18, Cu I 2(B)2 fragments present the coordination modes for the ligands B usually observed in the derivatives A, C and D. [7,[10][11][12] All the P-phenyl substituents point towards the cyano-ligands, which correspond to a preferred configuration of the ligands B in which the sterical constraints in the (Cu I )2(B) fragments are minimized. In addition, all the metric parameters of the dicationic (Cu I )2(B)2 cores of the derivatives 10-18 are very similar to those of the molecular clip A [7] and the metallacycles C-D (Table S4).…”

“…However, the Cu(I) molecular clip A presents a very specific molecular pre-organization (short intermetallic distances, strongly directional and convergent U-shape geometry) allowing to implement significantly these guiding rules via the formation of stabilizing interlinkers' interactions. [9][10][11] In the case of the syntheses of the compact metallacycles C and D (Scheme 1), the directionality of the rigid linkers used and the strength of the interlinkers' interactions induced (π-π or metallophilic interactions) imply a strong enthalpic stabilization and a negligible entropic cost, promoting the general and selective formation of these metallacycles. Therefore the series of results described herein highlights a novel aspect of such selfassembling processes, demonstrating most particularly the access to an unprecedented family of coordination-driven supramolecular metallacycles bearing FA walls.…”