The macrocyclic ligand conformational behavior in solution, solid-state structures and the photophysical properties of copper(I) cationic and neutral mononuclear complexes supported by tetradentate N, N'-dialkyl-2,11-diaza[3.3](2,6)-pyridinophane ligands N4 (R = H, Me,Bu, Bu,Pent, Pr, Ts) were investigated in detail. Steric properties of the alkyl group at the axial amine in theN4 ligand were found to strongly affect the conformational preferences and dynamic behavior in solution. Several types of conformational exchange processes were revealed by variable-temperature NMR and 2D exchange spectroscopy, including degenerative exchange in a pseudotetrahedral species as well as exchange between two isomers with different conformers of tri- and tetracoordinate N4 ligands. These exchange processes are slower for the complexes containing bulky alkyl groups at the amine compared to less sterically demanding analogues. A clear correlation is also observed between the steric bulk of the alkyl substituents and the photoluminescent properties of the derived complexes, with less dynamic complexes bearing bulkier alkyl substituents exhibiting higher absolute photoluminescence quantum yield (PLQY) in solution and the solid state: PLQY in solution increases in the order Me< Pent< Bu< Bu ≈Pr < Bu. The electrochemical properties of the cationic complexes [(N4)Cu(MeCN)]X (X = BF, PF) were also dependent on the steric properties of the amine substituent.

The dimeric pyranonaphthoquinones, “bis versions” of the naphtho[2,3‐c]pyran‐5,10‐dione moiety, comprises a group of antibiotics that have been isolated from a variety of sources including plants, bacteria, fungi, and insects. This review discusses the known naturally occurring dimeric pyranonaphthoquinones, their isolation and bioactivity, and synthetic approaches towards them that have helped to confirm their structures, as well as to resolve structural uncertainties such as stereochemistry. The major focus has been on the synthetic approaches adopted to complete the challenging total synthesis of the natural isolates and analogues.

Triboluminescent compounds that generate emission of light in response to mechanical stimulus are promising targets in the development of “smart materials” and damage sensors. Among triboluminescent metal complexes, rare-earth europium...

Direct translation of mechanical force into changes in chemical behavior on a molecular level has important implication not only for the fundamental understanding of mechanochemical processes, but also for the development of new stimuli-responsive materials. In particular, detection of mechanical stress in polymers via non-destructive methods is important in order to prevent material failure and to study the mechanical properties of soft matter. Herein, we report that highly sensitive changes in photoluminescence intensity can be observed in response to the mechanical stretching of cross-linked polymer films when using stable, (pyridinophane)Cu-based dynamic mechanophores. Upon stretching, the luminescence intensity increases in a fast and reversible manner even at small strain (< 50%) and applied stress (< 0.1 MPa) values. Such sensitivity is unprecedented when compared to previously reported systems based on organic mechanophores. The system also allows for the detection of weak mechanical stress by spectroscopic measurements or by direct visual methods.<br>

Highly sensitive mechanical stress detection is achieved by using dynamic Cu(i)-based mechanophores as cross-linkers.