Gold(I) and Platinum(II) Tetracenes and Tetracenyldiacetylides: Structural and Fluorescence Color Changes Induced by σ-Metalation

How to Stabilize Large Soluble (Hetero-)Acenes

The higher acenes and azaacenes (>(aza)heptacenes) are fascinating, yet elusive materials. Their reactivity and sensitivity increases concomitantly with their size. In recent years, confinement techniques, that is isolation of acenes in matrices and on surfaces, has surpassed solution-based chemistry with respect to accessing the larger (hetero)acenes at the price of the accessibility of no more than a couple thousands of molecules. Isolating acenes in bulk quantities and in processable form is vital for applications in organic electronics as well as from a viewpoint from basic research. In this Perspective, we will discuss after a short historical outline their degradation pathways, and then will selectively highlight recent efforts in stabilizing soluble (aza)acenes.

Non-covalent interactions (NCIs) in π-conjugated functional materials: advances and perspectives

The design and development of functional materials with real-life applications are highly demanding. Understanding and controlling inter- and intra-molecular interactions provide opportunities to design new materials. A judicious manipulation of the molecular structure significantly alters such interactions and can boost selected properties and functions of the material. There is burgeoning evidence of the beneficial effects of non-covalent interactions (NCIs), showing that manipulating NCIs may generate functional materials with a wide variety of physical properties leading to applications in catalysis, drug delivery, crystal engineering, etc. This prompted us to review the implications of NCIs on the molecular packing, optical properties, and applications of functional π-conjugated materials. To this end, this tutorial review will cover different types of interactions (electrostatic, π-interactions, metallophilic, etc.) and their impact on π-conjugated materials. Attempts have also been made to delineate the effects of weak interactions on opto-electronic (O-E) applications.

Oxidized divinyl oligoacene-bridged diruthenium complexes: bridged localized radical characters and reduced aromaticity in bridge cores

A series of bimetallic ruthenium vinyl complexes 1-5 bridged by oligoacenes were synthesized and characterized in this study. Comparative cyclic voltammetry results from 1-5 indicated that the first oxidation potential decreased gradually with the extension of conjugate ligands. Upon oxidation to singly oxidized species 1+-5+, rather small ν(CO) changes in the infrared (IR) spectra and the characteristic bands of metal-to-ligand charge transfer absorptions in the near IR (NIR) region predicted via time-dependent DFT calculations suggested that strong bridged ligands participate in redox processes. NIR absorptions were not observed in complexes 4+ and 5+ possibly because of instability in their twisted and noncoplanar geometry. Electron paramagnetic resonance results and spin density distribution demonstrated that the bridged localized degrees of 1+-5+ successively increased with the extension of oligoacene from benzene to tetracene. Further comparative analysis of neutral molecules and monocations to the aromaticity and π-electron density of bridge cores indicated a step-by-step transformation process from an aromatic to quinoidal radical upon oxidation.

Dinuclear gold(i) complexes: from bonding to applications

The last two decades have seen a veritable explosion in the use of gold(i) complexes bearing N-heterocyclic carbene (NHC) and phosphine (PR₃) ligands.

Solution versus solid-state dual emission of the Au(i)-alkynyl diphosphine complexes via modification of polyaromatic spacers

Single molecule luminophores capable of multiple emissions are essential for the development of new materials with unconventional photophysical behavior.

Cooperative supramolecular polymers with anthracene‒endoperoxide photo-switching for fluorescent anti-counterfeiting

Innovative technologies are highly pursued for the detection and avoidance of counterfeiting in modern information society. Herein, we report the construction of photo-responsive supramolecular polymers toward fluorescent anti-counterfeit applications, by taking advantage of multicycle anthracene‒endoperoxide switching properties. Due to σ-metalation effect, photo-oxygenation of anthracene to endoperoxide is proceeded under the mild visible light irradiation conditions, while the backward conversion occurs spontaneously at room temperature. Supramolecular polymers are formed with cooperative nucleation‒elongation mechanism, which facilitate fluorescence resonance energy transfer process via two-component co-assembly strategy. Fluorescence resonance energy transfer efficiency is delicately regulated by either light-triggered anthracene‒endoperoxide conversion or vapor-induced monomer–polymer transition, leading to high-contrast fluorescent changes among three different states. On this basis, dual-mode anti-counterfeiting patterns have been successfully fabricated via inkjet printing techniques. Hence, cooperative supramolecular polymerization of photo-fluorochromic molecules represents an efficient approach toward high-performance anti-counterfeit materials with enhanced security reliability, fast response, and ease of operation.

There is a continual pursuit for different ways to detect counterfeiting in today’s society. Here the authors show photo-responsive supramolecular polymers can be used in fluorescent anti-counterfeit applications, by taking advantage of multicycle anthracene‒endoperoxide switching properties.

Rise of Conjugated Poly-ynes and Poly(Metalla-ynes): From Design Through Synthesis to Structure-Property Relationships and Applications

Conjugated poly-ynes and poly(metalla-ynes) constitute an important class of new materials with potential application in various domains of science. The key factors responsible for the diverse usage of these materials is their intriguing and tunable chemical and photophysical properties. This review highlights fascinating advances made in the field of conjugated organic poly-ynes and poly(metalla-ynes) incorporating group 4-11 metals. This includes several important aspects of conjugated poly-ynes viz. synthetic protocols, bonding, electronic structure, nature of luminescence, structure-property relationships, diverse applications, and concluding remarks. Furthermore, we delineated the future directions and challenges in this particular area of research.

Reductive Coupling of Diynes at Rhodium Gives Fluorescent Rhodacyclopentadienes or Phosphorescent Rhodium 2,2'-Biphenyl Complexes

Reactions of [Rh(κ(2) -O,O-acac)(PMe3 )2 ] (acac=acetylacetonato) and α,ω-bis(arylbutadiynyl)alkanes afford two isomeric types of MC4 metallacycles with very different photophysical properties. As a result of a [2+2] reductive coupling at Rh, 2,5-bis(arylethynyl)rhodacyclopentadienes (A) are formed, which display intense fluorescence (Φ=0.07-0.54, τ=0.2-2.5 ns) despite the presence of the heavy metal atom. Rhodium biphenyl complexes (B), which show exceptionally long-lived (hundreds of μs) phosphorescence (Φ=0.01-0.33) at room temperature in solution, have been isolated as a second isomer originating from an unusual [4+2] cycloaddition reaction and a subsequent β-H-shift. We attribute the different photophysical properties of isomers A and B to a higher excited state density and a less stabilized T1 state in the biphenyl complexes B, allowing for more efficient intersystem crossing S1 →Tn and T1 →S0 . Control of the isomer distribution is achieved by modification of the bis- (diyne) linker length, providing a fundamentally new route to access photoactive metal biphenyl compounds.

Dual ligand-based fluorescence and phosphorescence emission at room temperature from platinum thioxanthonyl complexes

Platinum complexes with σ-bonded thioxanthonyl (Tx) ligands exhibit, on irradiation into the Tx π→π* band, dual Tx-based fluorescence and phosphorescence emission with phosphorescence quantum yields of up to 19% in fluid solution at room temperature.

Luminescent copper(i) halide and pseudohalide phenanthroline complexes revisited: simple structures, complicated excited state behavior

Despite their chemical simplicity, copper(i) phenanthroline halides appear to involve multiple states in the emission process and exhibit non-trivial photophysical properties.

Alkali/coinage metals – organolithium, organocuprate chemistry

Part 1 of this chapter reviews coordination compounds of the alkali metals that contain a carbon-metal bond, looking firstly at organolithiums involving simple silanes. The use of aryl, alkynyl and N-donor ligands is also discussed. Compounds of the coinage metals - copper, silver and gold - are discussed in Part 2 of the review. Discussion is broken down by metal, with copper being considered first. Compounds containing, among others, alkene, amido and phosphido ligands are discussed, along with the significant amount of work on carbene complexes. This interest in carbene complexes is also noted within the silver and gold sections that follow, with a large number of new compounds being described. Polymeric chains and networks containing silver centres have attracted considerable interest and are described, along with the luminescent properties of a selection of novel gold species. This part of the review is completed by coverage of mixed-coinage metal structures, where the systems are found to display luminescent properties. Here again, the compounds discussed contain at least one carbon-metal bond.

A unique non-catenane interlocked self-assembled supramolecular architecture and its photophysical properties

A novel, interlocked, self-assembled (M(2)L(2))(2) molecular architecture was constructed from an arene-Ru acceptor and a 1,4-di(pyridin-4-yl)buta-1,3-diyne donor. Two M(2)L(2) units, with cavities of ~7.21 Å, spontaneously interlock, with one unit encapsulating a twin in a non-catenane fashion. The dimeric host-guest complex thus formed is unique among two-dimensional self-assemblies and is stabilized by π-π interactions between the M(2)L(2) units.