Anomalous photophysics of bis(hydroxystyryl)benzenes: a twist on the para/meta dichotomy

The dianions of two isomeric bis(hydroxystyryl)benzenes show dramatically different photophysical properties.     

ErF3‐reiche ternäre Erbiumfluoride mit den schweren Alkalimetallen: I. KEr3F10 und RbEr3F10

ErF₃‐Rich Ternary Erbium Fluorides with the Heavy Alkali Metals: I. KEr₃F₁₀ and RbEr₃F₁₀ The conversion of erbium trifluoride (ErF₃) with chlorides of the heavy alkali metals (ACl; A = K, Rb and Cs) at 700–800 °C in tantalum capsules sealed by arc‐welding surprisingly results in the formation of ErF₃‐rich ternary alkali‐metal erbium(III) fluorides with the compositions AEr₃F₁₀ (A = K and Rb) or CsEr₂F₇, respectively. The first‐mentioned compounds are characterized by high coordination numbers at the alkali‐metal cation (CN(A⁺) = 15 and 16) as well as by a uniform surrounding of the Er³⁺ cation (CN = 8, square antiprism). In KEr₃F₁₀ (cubic, Fm3m; a = 1154.06(7) pm, Z = 8) eight (F1)^? anions always arrange as a cube, whose six faces are each capped by an Er³⁺ cation. These [(F1)₈Er₆]¹⁰⁺ groups constitute a cubic closest sphere‐packing with K⁺ cations in all of the tetrahedral interstices. The [Er₆(μ₃‐F1)₈]¹⁰⁺ units are interconnected via the remainder fluoride anions (F2) to build up a three‐dimensional framework so that the characteristic [ErF₈]^5? polyhedra (d(Er³⁺?F^?) = 220 – 235 pm) emerge. In RbEr₃F₁₀ (hexagonal, P6₃mc; a = 818.43(5), c = 1336.54(8) pm, Z = 4) the analogous [ErF₈]^5? polyhedra (d(Er³⁺?F^?) = 219 – 237 pm) initially convene to triple groups [Er₃F₁₉]^10? through cis‐edge condensation, which are then further connected via F^? corners to arrange as a two‐dimensional network perpendicular to the c axis. Finally, the cross‐linking of these layers is achieved by common F^? vertices again, such that large cavities apt to take up the Rb⁺ cations are formed. A second part of these series will report on the syntheses and crystal structures of the ErF₃‐poorer AEr₂F₇‐type representatives with A = K, Rb and Cs.     

Er3O2F5: Ein Erbiumoxidfluorid mit Vernier‐Struktur

Er₃O₂F₅: An Erbium Oxide Fluoride with Vernier‐Type Structure Attempts to synthesize multinary erbium‐trifluoride derivatives (e. g. Er₃F[Si₃O₁₀], Er₄F₂[Si₂O₇][SiO₄], CsEr₂F₇, and RbEr₃F₁₀) from mixtures of ErOF‐contaminated erbium trifluoride (ErF₃) itself and appropriate other components (such as Er₂O₃ and SiO₂ or CsF and RbF, respectively) frequently resulted in the formation of pale pink, transparent, lath‐shaped single crystals of Er₃O₂F₅ (orthorhombic, Pnma; a = 562.48(5), b = 1710.16(14), c = 537.43(4) pm; Z = 4) as by‐product, typically after seven days at 800 °C and regardless of the applied reaction‐container material (evacuated torch‐sealed silica or silica‐jacketed arc‐welded tantalum capsules). Its crystal structure, often described as a vernier‐type arrangement consisting of two interpenetrating and almost misfitting lattices (ErOF and ErF₃), contains two crystallographically different Er³⁺ cations in the eight‐ and seven‐plus‐one‐fold anionic coordination of bicapped trigonal prisms. Whereas (Er1)³⁺ carries four O^2? and F^? anions each, (Er2)³⁺ resides in the neighbourhood of only two O^2?, but five plus one F^? anions. As the main structural feature, however, one can consider O^2?‐centred (Er³⁺)₄ tetrahedra which share common edges to form linear double strands of the composition . Running parallel to the [100] direction and assembling like a hexagonal closest rod‐packing, their electroneutralization and three‐dimensional interconnection is achieved by three crystallographically independent F^? anions (d(F^??Er³⁺) = 221 ? 251 plus 281 pm) in three‐ and two‐plus‐two‐fold coordination of the Er³⁺ cations, respectively.     

Hydroxy-cruciforms

The synthesis of hydroxy-cruciforms 7 and 8 and their dramatically varying photophysical properties upon exposure to amines are reported.     

Hydroxydialkylamino cruciforms: amphoteric materials with unique photophysical properties

Two amphoteric cruciforms 6 and 7 (XF; 4,4'-[(1E,1'E)-(2,5-bis{[4-(dibutylamino)phenyl]ethynyl}-1,4-phenylene)bis(ethene-2,1-diyl)]diphenol, 4,4'-[{2,5-bis[(E)-4-(dibutylamino)styryl]-1,4-phenylene}bis(ethyne-2,1-diyl)]diphenol) were prepared by a Horner reaction followed by a Sonogashira coupling and subsequent deprotection. The XFs display significant changes in absorption and emission when exposed to trifluoroacetic acid, tetrabutylammonium hydroxide, and metal triflates. The substitution pattern of 6 and 7 leads to spatial separation of the frontier molecular orbitals, which allows the HOMO or LUMO of the XF to be addressed independently by acidic or basic agents. XF 6, which has hydroxyl groups on the styryl axis, displays changes in emission color upon exposure to ten amines in eight different solvents. The change in fluorescence upon the addition of amines was analyzed by linear discriminant analysis. These XFs may have potential in sensor applications for metal cations and amines.     

Alkene Metathesis – A Tool for the Synthesis of Conjugated Polymers

Alkene metathesis is a superb methodology. We report the progress using alkene metathesis in the synthesis of polymeric organic semiconductors. Three classes of polymers have been synthesized using acyclic diene metathesis (ADMET) or ring opening metathesis polymerization (ROMP), viz., poly(acetylene)s (PA), poly(arylene‐vinylene)s (PAV), and organometallic polymers. For PAs, ROMP of cyclooctatetraenes is best, whereas for PAV, both ADMET and indirect and direct ROMP are viable. Metathesis performs flawlessly with the correct monomers, as molybdenum and particularly the robust Ru carbenes demonstrate. When performing ROMP, one is often rewarded with structurally uniform polymers that can display very low polydispersities. Overall, metathesis is a powerful tool for the preparation of semiconducting polymers.     

Aldehyde-appended distyrylbenzenes: amine recognition in water

Change in water: Aqueous solutions of aldehyde-substituted, water-soluble distyrylbenzenes reacted with amines to give imines or aminals with dramatically changed fluorescence. This approach allowed the detection and recognition of amines in water (see figure).     

Synthesis and optical properties of diaza- and tetraazatetracenes

A series of functionalized diaza- and tetraazatetracenes was synthesized, either by condensation of an aromatic diamine with an ortho-quinone/diethyloxalate followed by chlorination with POCl(3) to give diazatetracenes or by palladium-catalyzed coupling of a phenylenediamine with various 2,3-dichloroquinoxalines to give tetraazatetracenes (after oxidation with MnO(2)). Representative examples included halogenated and nitrated derivatives. The optical properties of these azatetracenes were discussed with respect to their molecular structures and substitution patterns. The diazatetracenes and tetraazatetracenes formed two different groups that had significantly different electronic structures and properties. Furthermore, 1,2,3,4-tetrafluoro-6,11-bis((triisopropylsilyl)ethynyl)benzo[b]phenazine was synthesized, which is the first reported fluorinated diazatetracene. Single-crystal X-ray analysis of this compound is reported.     

A Molecular Paddlewheel with a Sliding Organometallic Latch: Syntheses,X‐Ray Crystal Structures and Dynamic Behaviour of [Cr(CO)3{η6‐2‐(9‐triptycyl)indene}], and of [M(CO)3{η5‐2‐(9‐triptycyl)indenyl}] (M=Mn,Re)

Metal clamping in operation! Deprotonation of [η⁶‐2‐(9‐triptycyl)indene]tricarbonylchromium induces a haptotropic shift of the organometallic fragment from the six‐membered to the five‐membered ring, as in a→b . In the anion, rotation of the molecular paddlewheel is blocked by the bulky tripod. X‐ray crystal structures provide pictures of the system in both its “ON” and “OFF” states.