Photochromic Thienylpyridine–Bis(alkynyl)borane Complexes: Toward Readily Tunable Fluorescence Dyes and Photoswitchable Materials

Given that pyrene represents one of the most versatile chromophores, the development of new selective routes for its functionalization and tuning of its emission properties is highly desirable. Pyrene‐based BN Lewis pair (LP)‐functionalized polycyclic aromatic hydrocarbons (PAHs) were prepared by regioselective Lewis base‐directed electrophilic aromatic substitution. The requisite 1,6‐dipyridylpyrene ligands were accessed by Suzuki–Miyaura cross‐coupling of 1,6‐bis(pinacolatoboryl)pyrenes with 2‐bromopyridine derivatives. Subsequent electrophilic borylation with BCl3 in the presence of AlCl3 and 2,6‐di‐tert‐butylpyridine as a hindered base produced the dichloroborane complexes, which were then in situ reacted with diphenyl or diethyl zinc. The presence or absence of alkyl chains in the 3,8‐positions of the pyrene moiety determined the position of the B−C bond formation (2,7 in the non‐K region versus 5,10 in the K region) and thereby also the size of the BN heterocycle (five‐ versus six‐membered). The impact of the regioisomeric borylation on the electrochemical, photophysical and structural properties was investigated and the conclusions supported by theoretical calculations. The rapid synthesis of derivatives that are borylated in the K region also suggests strong potential for the development of pyrene derivatives that are otherwise difficult to access.

Section: Resultsmentioning

confidence: 99%

Controlling the Optoelectronic Properties of Pyrene by Regioselective Lewis Base‐Directed Electrophilic Aromatic Borylation

Vanga

Lalancette

Jäkle

2019

“…To synthesize the polymer 8, reversible addition/fragmentation chain-transfer polymerization (RAFT) conditions were used to polymerize the acrylate-functionalized monomer (7). The side-chain dithienylethene polymer was prepared by using the side-chain transfer reagent (9) in the presence of a radical initiator azobisisobutylnitrile (AIBN) in deoxygenated benzene at 80 8C (Figure 3). The reaction was monitored by 1 H NMR spectroscopy, and the formation of the polymer increased linearly with time, which is characteristic of a controlled polymerization.…”

Section: Resultsmentioning

confidence: 99%

“…Ultimately, this could reveal new discoveries for photochromic reactivity. The incorporation of p-block elements into DTE systems are particularly well suited for optoelectronic materials and sensing, [7][8][9][10][11][12] Abstract: Within the past decade photochromic materials, specifically dithienylA C H T U N G T R E N N U N G ethenes (DTEs), have received increased interest because of their ability to function as potential photoswitchable molecular devices and optical memory storage systems. Current research in this area has focused on incorporating organic architectures to functionalize the DTE framework and alter the resulting photophysical properties; however, their syntheses are often not trivial.…”

Section: Introductionmentioning

confidence: 99%

A Versatile Dithienylethene‐Functionalized Ph‐Diazabutadiene (DAB) Ligand: From Photoswitchable Main‐Group Molecules to Photochromic Polymers

Price

Ragogna

2013

Within the past decade photochromic materials, specifically dithienylethenes (DTEs), have received increased interest because of their ability to function as potential photoswitchable molecular devices and optical memory storage systems. Current research in this area has focused on incorporating organic architectures to functionalize the DTE framework and alter the resulting photophysical properties; however, their syntheses are often not trivial. In this context, we have designed a simple and versatile diimine (2) containing adjacent 2,5-dimethyl(thienyl) rings in the backbone. This redox active diimine (2) acts as a precursor to a novel photochromic ligand and has been used to coordinate to both boron and phosphorus elements, along with the synthesis of a phosphorane-side-chain functionalized polymer without further functionalization to the parent DTE framework. A study of the resulting photochromic properties of these compounds revealed that 1) the UV-visible absorption spectra of the closed-ring isomer were dependent of the element present in the N,N'-chelating pocket and 2) incorporating the dithienylethene into a side-functionalized phosphorane polymer greatly increased the closed-/open-ring reversibility and decreased the formation of by-products.

“…Among the well‐established photochromic molecules, dithienylethene (DTE) derivatives, which can realize the switching of the molecules between a non‐conjugated “open” form and a conjugated “closed” form through specific wavelength light irradiation, is one of the most widely investigated systems owing to their rapid response, excellent fatigue‐resistance and high thermal stability. Through proper molecular design, such as the functionalization of the aromatic backbone or extension of the π‐conjugation on peripheral diaryl pendants, numerous photo‐switchable DTE derivatives with intriguing photochromic properties have been reported . Both experimental and theoretical studies demonstrated that the photocyclization reaction of DTE can proceed through both singlet and triplet pathways .…”

Section: Introductionmentioning

confidence: 99%

Photoisomerization of Pt^II Complexes Containing Two Different Photochromic Chromophores: Boron Chromophore versus Dithienylethene Chromophore

Shi

Wang

et al. 2019

In order to examine competitive photoisomerization, a series of novel photochromic PtII molecules that contain both dithienylethene (DTE) and B(ppy)Mes2 units (ppy=2‐phenylpyridine, Mes=mesityl) were successfully synthesized and fully structurally characterized. Their photochromic properties were examined by UV/Vis, emission and NMR spectroscopy. It was found that the DTE unit in all three compounds is the preferred photoisomerization site, exhibiting reversible photochromism with irradiation. The B(ppy)Mes2 unit does not undergo photoisomerization in these molecules, but likely enhances the photoisomerization quantum efficiency of the DTE moiety through the antenna effect. Extended irradiation with UV light leads to the rearrangement of the ring‐closed isomers of DTE. TD‐DFT computational studies indicate that the DTE photocyclization proceeds via a triplet pathway through an efficient energy transfer process.