Conformational and Electronic Engineering of Twisted Diphenylacetylenes

Abstract

Three tethered diphenylacetylene derivatives were prepared by alkyne metathesis. In these cycles, the twist angle between the two benzene rings is variable and determined by the nature of the linker. The engineering of the twist angle leads to a change of the UV−vis spectra of the cycles. The larger the twist angle in the macrocycles, the more blue shifted their λ max (UV−vis), the lower their fluorescence quantum yield, and the lower field shifted their 13 C NMR signals of the alkyne carbons are.

Synthesis of a Strained Acetylenic Macrocycle Incorporating a para‐Oligo[2]cruciform Bridge Bent over Nanoscopic Dimensions: Structural, Electronic, Spectroscopic, and Ion‐Sensing Properties

“…The temperature dependence of the UV/Vis spectra of 13 and 14 suggests a slight energetic preference for all‐planar conformations with optimal conjugation at lower temperatures, whereas the lower magnitude of the ${E{{{\rm opt}\hfill \atop {\rm g}\hfill}}}$ changes is consistent with reduced conformer conjugation differences expected for the acyclic precursors 48. The conclusion that relative TIPSA‐substituted phenyl rotations lie at the heart of the variable temperature (VT)‐UV/Vis phenomena in 1 , 13 , and 14 is also consistent with the finding that increasing the inter‐ring dihedral angle of sterically constrained bridged 1,2‐diphenylethynes causes an increase in the solution ${E{{{\rm opt}\hfill \atop {\rm g}\hfill}}}$ 49…”

“…[48] The conclusion that relative TIPSA-substituted phenyl rotations lie at the heart of the variable temperature (VT)-UV/Vis phenomena in 1, 13, and 14 is also consistent with the finding that increasing the inter-ring dihedral angle of sterically constrained bridged 1,2-diphenylethynes causes an increase in the solution E opt g . [49] Spectroscopic metal-ion-binding properties of 1 and 13: The highly sterically congested environment about the terpyridine binding site of 1 would be expected to block the formation of [M(1) 2 ] n + complexes, and even enforce ion-size restrictions resulting in selectivity for particular solvent-ligated metal ions. We therefore carried out spectroscopic investigations of the metal-ion-binding behavior of 1 as well as the acyclic precursor 13 for comparison, in order to obtain some qualitative insight into the metal complexation properties of this structurally unusual ligand.…”

Reply

“…It can be interpreted in terms of DPA deplanarization synchronous to the PBI disaggregation process. This observation indicates the freeze of the DPA structure in dimers of dyad 7 in contrast to its free rotatability in the monomeric state 43…”

Quadruple π Stack of Two Perylene Bisimide Tweezers: A Bimolecular Complex with Kinetic Stability

“…This observation indicates the freeze of the DPA structure in dimers of dyad 7 in contrast to its free rotatability in the monomeric state. [43] The absorption variations recorded in time intervals of 15 minutes (Figure 4) share several well-defined isosbestic points at 545, 477, 463, 450, and 266 nm, indicative of the disassembly process between only two explicit species, that is, the dimer and monomer of dyad 7. Thus, the dimer dissociation process can be regarded as a first-order fragmentation reaction.…”