Jingcao Dai

Fluorescent and photochromic bifunctional molecular switch based on a stable crystalline metal-viologen complex.

An air-stable photoresponsive viologen molecular system is constructed based on a three-fold accordion interpenetrating packing arrangement. The fluorescent modulation process is coupled with a photochromic reaction via energy and electron transfer between the adjacent donor and acceptor groups.

Copper based metal–organic molecular ring with inserted Keggin-type polyoxometalate: a stable photofunctional host–guest molecular system

Keggin polyphosphotungstate cluster was captured by a porous molecular ring with light sensitizing TPT molecules as connectors and copper ions as nodes. The self-assembly reaction gives a stable host-guest supramolecular system, demonstrating efficient heterogeneous photocatalytic behavior for the degradation of methyl orange in near-neutral conditions.

Synthesis and structure of a mixed crystal containing tris(4-pyridiniumyl)-1,3,5-triazine and benzenetetracarboxylate ions: constructing a new photochromic molecular system viaself-assembly

A new type of photochromic supramolecule is designed and synthesized via the suitable combination of two nonphotoactive organic molecules tpt and btec. The connections built by strong intermolecular forces provide the possibility for contact electron transfer. Reversible color changes of the molecular switch are observed upon exposure to light irradiation.

A hybrid metal phosphate–phosphite material grafted with electron deficient organic components showing interesting fluorescent and photosensitive properties

A new hybrid organic zinc phosphate–phosphite with a tris (4-pyridyl) triazine molecule embedded in the cavity of an extra-large 24-ring channel has been synthesized and characterized. A strong luminescence emission is observed, which is due to the close packed array of organic ligands. The covalent coupling of fluorescent and photochromic components builds a novel phosphate-based photoactive dyad system.

Highly stable photochromic crystalline material based on a close-packed layered metal–viologen coordination polymer

Suitable combination of organic fragments N-(3-carboxyphenyl)-4,4′-bipyridinium and m-benzene dicarboxylate affords a new type photochromic metal–viologen coordination polymer with close packed arrangements. The aggregates build an interesting stable crystalline framework showing long lived color constancy. Repeating cycles of reversible color changes are observed for the molecular switch in air upon photoirradiation.

Synthesis of a 3D photochromic coordination polymer with an interpenetrating arrangement: crystal engineering for electron transfer between donor and acceptor units

A new photochromic coordination network is constructed via the combination of viologen and carboxylate fragments. Close packing of the two-fold diamond-like interwoven mode creates electron transfer bridges for the acceptor and donor components. Radicals are generated upon photoirradiation and are accompanied by a color change from yellow to blue-green.

Molecular packing, crystal to crystal transformation, electron transfer behaviour, and photochromic and fluorescent properties of three hydrogen-bonded supramolecular complexes containing benzenecarboxylate donors and viologen acceptors

An investigation into the relationship between structures of three D–A supramolecular systems and their photoresponsive characteristics is presented. Compound 1 [H2CPBPY]·[H2BTEC] and compound 2 [HCPBPY]2·[H2BTEC]·5H2O are prepared with the same starting materials at different pH values and characterized by single crystal X-ray diffraction, powder X-ray diffraction, UV-vis, IR and ESR spectra. Electron-deficient CPBPY moieties and electron-donating BTEC units are linked by hydrogen-bonds and π–π stacking interactions to form the donor–acceptor systems. Under light irradiation, photoactivated electrons can transfer from the donor to the acceptor units in both 1 and 2, giving rise to a long-lived charge-separated state and accompanying an interesting color changing phenomenon. Crystals of 2 allowed to dehydrate at elevated temperature undergo single-crystal to single-crystal transformation to yield 3 [HCPBPY]2·[H2BTEC], accompanied by a drastic change in structural arrangements. For the photocoloration character, compound 1 shows a faster photoresponsive rate than 2 and 3. For the fluorescence properties, compound 1 and 2 both exhibit photoluminescence emission centered at 400 nm, whereas 3 exhibits photoluminescence emission at 520 nm, showing a significant red shift of 120 nm. Their different photoactive characters can be attributed to the connecting, packing modes and the valence states of the functional D–A moieties.

Discovery of polymorphism-dependent emission for crystalline boron-dipyrromethene dye

4-Methoxycarbonylphenyl-substituted BODIPY (boron-dipyrromethene) dye gives, in the solid state, three polymorphs. In spite of the absence of any strong intermolecular interactions in all crystalline forms, the three polymorphs show different photoluminescence properties. This behavior highlights the importance of molecular arrangements of the BODIPY moieties in the crystalline state in perturbing their photophysical properties.

Direct observation of conformational change of adipate dianions encapsulated in water clusters

Two novel hydrated adipate dianions including (adip)aaa·(H2O)16 and (adip)gag·(H2O)20 (adip = dianion of adipic acid, aaa = anti–anti–anti and gag = gauche–anti–gauche) were observed in two silver-based cationic hosts. They not only reveal the precise arrangement of water clusters around the carboxylate groups and aliphatic chains of adipate dianions, but show the conformational change of adipate dianions in water clusters, for the first time.

A stimuli-responsive zinc-based chain framework constructed via metal–ligand directed assembly

A new stable 1D photo-responsive coordination polymer is constructed via introducing a viologen side group to the metal–carboxylate framework. This structural arrangement creates an interesting dual stimuli-responsive molecular system. Coupled with the fluorescence modulation process, a photochromic reaction is induced by energy and electron transfer between the neighbouring donor and acceptor units.