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Anion-responsive sign inversion of circularly polarized luminescence (CPL) was successfully achieved by N

Nine nona-coordinated Eu(III) complexes (1-9) studied here have three unsymmetric β-diketonate ligands and one chiral Ph-Pybox ligand, which can produce eight possible coordination isomers, depending on the position of the three unsymmetric β-diketonate ligands. Substituents on the β-diketonate ligands cause a rational structural rearrangement upon crystallization. Substituents with higher polarity, including -CN, -F, -Cl, -Br, -OMe, and -OEt, employ intercomplex hydrogen bonding to generate an association complex through structural rearrangement upon crystallization. Substituents with lower polarity, including -CF3, -SMe, and -Me, cause the most energetically favorable isomer to crystallize directly from solution. These two crystal structures exhibit well-resolved f-f emission lines with characteristic Stark splitting structures. This work revealed that the configuration of the Eu(III) complexes in solution can be determined by systematic comparison of their Stark splitting structures to those obtained from the solid phase using density functional theory (DFT)-based predictions combined with circular dichroism data.

Three new tetranuclear europium(III) alternating circular helicates, (2-PhRRRR/2-PhSSSS) [(R)- or (S)-Ph-Pybox]4EuIII4(BPP)6, (2-iPrRRRR/2-iPrSSSS) [(R)- or (S)-iPr-Pybox]4EuIII4(BPP)6, and (3-PhRRRR/3-PhSSSS) [(R)- or (S)-Ph-Pybox]4EuIII4(BHP)6, are presented with their structural and chiroptical characterization (BPP and BHP = bis-β-diketonates; Pybox = chiral bis(oxazolinyl) pyridine ligand). X-ray crystallographic analysis revealed that different extents of interligand-contacting interactions between bis-β-diketonates and Pybox ligands produce different bis-β-diketonates arrangements around four EuIII ions and, thus, their specific symmetry in the final tetranuclear complexes. 2-PhRRRR/2-PhSSSS and 3-PhRRRR/3-PhSSSS are recognized as D2-symmetry, while 2-iPrRRRR/2-iPrSSSS self-assemblies possess pseudo C2h-symmetry. Due to different molecular symmetry, 2-PhRRRR/2-PhSSSS and 2-iPrRRRR/2-iPrSSSS crystals display different ligands orientation in their EuIII coordination spheres. The presence of pseudo σh-mirror symmetry in 2-iPrRRRR/2-iPrSSSS promotes a pair of distinguishable EuIII geometries. All the chiral self-assemblies exhibit almost identical photoluminescence emission spectra patterns of f-f transitions in the EuIII core. The EuIII self-assemblies exhibit intense CPL with different observed |glum| values (2-PhRRRR/2-PhSSSS ∼ |0.31|, 2-iPrRRRR/2-iPrSSSS ∼ |0.08|, 3-PhRRRR/3-PhSSSS ∼ |0.31| in chloroform).

Imidazole-based ditopic ligands bearing two chiral alkyl groups (LRR, LSS, and LRS) were synthesized. The ligands formed Pd2L4 helicates with palladium ions (Pd2+). Self-sorting occurred between LRR and LRS to form (Pd2+)2(LRR)4 and (Pd2+)2(LRS)4 homoligand assemblies, whereas mixing of LRR and LSS with Pd2+ gave a near statistical mixture.

The reactants of AQH–CH2CN are converted into AQ and CH3CN in sustainable electrocatalytic chain reactions, successfully achieving catalytic electron-triggered charge-transfer (CT) complex formation.

New C3-symmetric imidazole ligands were designed with phosphine and phosphine oxide linkers (LP and LPO, respectively) to demonstrate a dual-triggered dynamic closed coordination cage. Both LP and LPO form discrete Zn4L4-closed cages (1P and 1PO, respectively) with excellent selectively for BPh4-, whereas 1P and 1PO encapsulate neither a slightly larger size anion [B(C6H4CH3)4-] nor smaller size anions (BF4-, PF6-, SbF6-, and OSO2CF3-). 1PO exhibits more negative enthalpy and entropy changes upon anion encapsulation, thus releasing almost all of the encapsulated anions at high temperature (343 K) (trigger 1: BPh4-⊂1PO ⇄ 1PO + BPh4-). In contrast 1P has less negative enthalpy and entropy changes, thus preserving the captured anion over a wide range of temperatures (298 K to 343 K). The 1P cage can be quantitatively oxidized to the 1PO cage by a mild oxidant (Ox. = H2O2), and therefore the captured anion can be released by a redox triggering event (trigger 2: BPh4-⊂1P + Ox. → 1PO + BPh4-).

Nine nona-coordinated Eu(III) complexes (1–9) studied here have three unsymmetric β-diketonate ligands and one chiral Ph-Pybox ligand, which can produce eight possible coordination isomers, depending on the position of the three unsymmetric β-diketonate ligands. Substituents on the β-diketonate ligands cause a rational structural rearrangement upon crystallization. Substituents with higher polarity, including −CN, −F, −Cl, −Br, −OMe, and −OEt, employ intercomplex hydrogen bonding to generate an association complex through structural rearrangement upon crystallization. Substituents with lower polarity, including −CF3, −SMe, and −Me, cause the most energetically favorable isomer to crystallize directly from solution. These two crystal structures exhibit well-resolved f–f emission lines with characteristic Stark splitting structures. This work revealed that the configuration of the Eu(III) complexes in solution can be determined by systematic comparison of their Stark splitting structures to those obtained from the solid phase using density functional theory (DFT)-based predictions combined with circular dichroism data.

Pyrene-based chiral ligands (LR and LS) consisting of two chiral imidazole sidearms at the 1,8-positions first form pyrene-bridged oligomers [(L(R or S))3(Zn2+)n], which are chiroptically inactive, with a low concentration of zinc ions (Zn2+). Upon addition of more Zn2+, chiroptically active coordination helicates ([(L(R or S))3(Zn2+)2]) are formed. The stepwise assembly process successfully facilitated an "off-off-on" chiroptical switching process of a pyrene luminophore controlled by the concentration of Zn2+. The resulting pyrene-bridged helicates exhibit high performance in terms of a dissymmetry factor of circular dichroism (|gCD| = 0.006) and circularly polarized luminescence (|gCPL| = 0.01).

Monodentate ligand binding is facilitated by supramolecular chirality transformations from propeller-shaped chirality into single-twist chirality by altering the self-assembly of C3-symmetric chiral ligands. The C3-symmetric chiral ligands (ImR3Bz and ImS3Bz) contain three chiral imidazole side arms (ImR and ImS) at the 1,3,5-positions of a central benzene ring. Upon coordination to zinc ions (Zn2+), which have a tetrahedral coordination preference, the C3-symmetric chiral ligands assemble, in a stepwise manner, into a propeller-shaped assembly with a general formula (Im(RorS)3Bz)4(Zn2+)3. In this structure each Zn2+ ion coordinates to the three individual imidazole side arms. The resulting assembly is formally coordinatively unsaturated (coordination number, n = 3) and capable of accepting monodentate co-ligands (imidazole: ImH2) to afford a coordinatively saturated assembly [(ImH2)3(ImR3Bz)4(Zn2+)3]. The preformed propeller-shaped chirality is preserved during this transformation. However, an excess of the monodentate co-ligand (ImH2/Zn2+ molar ratio of ∼1.7) alters the propeller-shaped assembly into a stacked dimer assembly [(ImH2)m(ImR3Bz)2(Zn2+)3] (m = 4–6) with single-twist chirality. This switch alters the degree of enhancement and the circular dichroism (CD) pattern, suggesting a structural transition into a chiral object with a different shape. This architectural chirality transformation presents a new approach to forming dynamic coordination-assemblies, which have transformable geometric chiral structures.

Long-range chirality recognition between the two chiral guest ligands can be tuned based on the helix distances (dLn–Ln = 11.5 and 14.0 Å) of bis-diketonate bridged dinuclear lanthanide complexes (2Th and 3Th, respectively) used as mediators. Both 2Th and 3Th form one-dimensional (1D) helical structures upon terminal binding of two chiral guest co-ligands (LR or LS). Long-range chiral self-recognition is achieved in self-assembly of 2Th with LR and LS to preferentially form homochiral assemblies, 2Th-LR·LR and 2Th-LS·LS, whereas there is no direct molecular interaction between the two guest ligands at the terminal edges. X-ray crystal structure analysis and density functional theory studies reveal that long-range chiral recognition is achieved by terminal ligand-to-ligand interactions between the bis-diketonate ligands and chiral guest co-ligands. Conversely, in self-assembly of 3Th with a longer helix length, statistical binding of LR and LS occurs, forming heterochiral (3Th-LR·LS) and homochiral (3Th-LR·LR and 3Th-LS·LS) assemblies in an almost 1 : 1 ratio. When phenyl side arms of the chiral guest co-ligands are replaced by isopropyl groups (L′R and L′S), chiral self-recognition is also achieved in the self-assembly process of 3Th with the longer helix length to generate homochiral (3Th-L′R·L′R and 3Th-L′S·L′S) assemblies as the favored products. Thus, subtle modification of the chiral guests is capable of achieving over 1.4 nm-range chirality recognition., Long-range chirality recognition between the two chiral guest ligands can be tuned based on the helix distances (dLn–Ln = 11.5 and 14.0 Å) of bis-diketonate bridged dinuclear lanthanide complexes (2Th and 3Th, respectively).

This work reports on the structural and photophysical characterization of D4-symmetrical octanuclear circular LnIII helicates, [(R)- or (S)-iPr-Pybox]8(LnIII)8(THP)8 (where Ln = Eu and Tb, THP = trianionic tris-β-diketonate, and iPr-Pybox = chiral bis(4-isopropyl-2-oxazolinyl)pyridine). X-ray crystallographic analysis revealed that the octanuclear circular helicate possesses square antiprism architecture and consists of four [(R)- or (S)-iPr-Pybox]2LnIII2(THP)2 asymmetric units arranged in a closed ring form. Ligand-to-ligand interactions between the THP and the iPr-Pybox ligands have successfully directed formation of enantiopure, homoconfigurational (Δ,Δ,Δ,Δ,Δ,Δ,Δ,Δ)-R and (Λ,Λ,Λ,Λ,Λ,Λ,Λ,Λ)-S isomers. All of the nonacoordinated LnIII ions are identical and exhibit a distorted capped square antiprism (CSAP) geometry. Upon excitation of the ligand absorption band (λ = 360 nm), the circular helicates display characteristic EuIII (red, 5D0 → 7FJ, J = 0-4) or TbIII (green, 5D4 → 7FJ, J = 6-3) core f-f luminescence. The overall emission quantum yields of the circular EuIII and TbIII helicates are 0.145 and 0.0013, respectively, in chloroform. The EuIII and TbIII complexes exhibit remarkable circularly polarized luminescence (CPL) activity at their magnetic dipole transition with observed luminescence dissymmetry factors |glum| of 1.25 (5D0 → 7F1, λ = 592 nm) and 0.25 (5D4 → 7F5, λ = 541 nm), respectively. Exceptional |glum| values of the circular EuIII helicates highlight the visible intensity difference between left and right circularly polarized emissions of R and S isomers in chloroform and PMMA thin film.

Three new tetranuclear europium(III) alternating circular helicates, (

Here, we show that charge-transfer interactions determine whether donor and acceptor ditopic ligands will associate in a complementary or self-complementary fashion upon metal-ion clipping. Anthracene-based (

Imidazole-based ditopic ligands bearing two chiral alkyl groups (LRR, LSS, and LRS) were synthesized. The ligands formed Pd2L4 helicates with palladium ions (Pd2+). Self-sorting occurred between LRR and LRS to form (Pd2+)2(LRR)4 and (Pd2+)2(LRS)4 homoligand assemblies, whereas mixing of LRR and LSS with Pd2+ gave a near statistical mixture.

We report on the design and synthesis of triscyclometalated iridium (Ir) complexes that contain aryloxy groups at the end of diamino linkers, which exhibit an extraordinarily long-emission lifetime, and were prepared by regioselective substitution reactions of

As an effort to integrate natural products chemistry and coordination chemistry, a diastereomeric pair of chiral alkaloidal manifolds composed of a bispyrrolidinoindoline (BPI) framework was design...

A homoleptic zinc(II) helicate organized by a pair of achiral dipyrromethene ligands through zinc(II) coordination was synthesized to evaluate the chiroptical properties. This zinc complex showed strong exciton-coupled chiroptical responses from the helical configuration with a large absorption dissymmetry factor |gabs | (up to 0.20). More importantly, intense polarized luminescence in the far-red region (700-850 nm) with a fluorescence quantum yield ΦFL of 0.23 was observed for this helicate with a dissymmetry factor |glum | of 0.022, the largest value among rare-earth- and precious-metal-free small molecules. These unprecedentedly large g values were supported by theoretical calculations.

The potential use of circularly polarized luminescence for object identification in a sensor application is demonstrated. New luminescence probes using pyrene derivatives as sensor luminophores were developed. (R,R)-Im2 Py and (S,S)-Im2 Py contain two chiral imidazole moieties at 1,6-positions through ethynyl spacers (angle between spacers ca. 180°). The probe molecules spontaneously self-assemble into chiral stacks (P or M helicity) upon coordination to metal ions with tetrahedral coordination (Zn2+ ). The chiral probes display neither circular dichroism (CD) nor circularly polarized luminescence (CPL) without metal ions. However, (R,R)-Im2 Py and (S,S)-Im2 Py exhibit intense chiroptical activity (CD and CPL) upon self-assembly with Zn2+ ions. (R,R)-Im2 Py and (S,S)-Im2 Py with chemical stimuli-responsibility allow sensing using the CPL signal as detection output, enabling us to discriminate between a signal from the target analyte and that from non-target species.

This work demonstrates a methodology for the evaluation of circularly polarized luminescence of a chiral europium(III) (EuIII) complex species in an ensemble system. The chiral EuIII complex species consists of chiral bis(oxazolinyl)pyridine [(R)- or (S)-iPr-Pybox] and β-diketonate ligands with a pendant nitro group (DK-NO2). The pendant NO2 group in [iPr-Pybox](EuIII)(DK-NO2)3 (monometallic EuIII species) coordinates to the EuIII center of another EuIII complex, giving rise to the generation of a chiral EuIII ensemble consisting of mono-, di-, and the other oligomeric EuIII species, {[iPr-Pybox](EuIII)(DK-NO2)3}n. The luminescence dissymmetry factors (glum) of the chiral EuIII ensemble have been successfully determined by using a commercially available fluorescence spectrophotometer attached with a rotatable λ/4 filter and a fixed linearly polarized plate. This study suggests that the chiral EuIII ensemble in solution displays a large circularly polarized luminescence (|glum| = 0.19) as compared to that of a reference monometallic complex [iPr-Pybox](EuIII)(DK-CN)3 (|glum| = 0.11–13). The larger glum is primarily attributed to the contribution of the dimetallic EuIII species exhibiting a high degree of circular polarization in luminescence (glum2 = 0.27) in the ensemble. Conversely, a large linearly polarized component was observed in luminescence from the chiral EuIII ensemble in the solid state (KBr pellet).

The structure and electronic features of neutral and positively charged pyrene and perylene derivatives were explored. The radical cation of 1,3,6,8-tetraarylpyrene 1 was examined by ESR, UV-vis-NIR spectroscopy and theoretical calculations. The addition of 2 equiv of oxidant to 1 resulted in the formation of dication 12+. The single-crystal X-ray structure of 12+ proved that the aromatic part relocates from biphenyl unit to naphthyl unit upon 2e- oxidation of 1. We have also investigated the oxidation processes of 3,9-diarylperylene 2 and 3,10-diarylperylene 3. The radical cations of 2・+ and 3・+ showed ESR signals and the spin densities were proven to delocalize at 3,4,9,10-positions. In the case of doubly charged 3,9-diarylperylene, we could find the anthracene structure in the core, while the phenanthrene skeleton appeared in two-electron oxidized 3,10-diarylperylene. Finally we validated this phenomenon to apply for the higher analogue terrylene, discovering its large aromaticity relocation upon the 2e- oxidation.

Circular polarized luminescence (CPL) is useful for advanced optical devices. However, it is difficult to achieve strong emission and high CPL properties at the same time. Herein, we synthesized a bisbutadiyne bridged azahelicene dimer with a figure-eight shape, which exhibited both high fluorescence quantum yield and the g value. The enhancement is due to the rigid conformation of the dimer.

This work demonstrates a new nonconventional ligand design, imidazole/pyridine-based nonsymmetrical ditopic ligands (1 and 1S ), to construct a dynamic open coordination cage from nonsymmetrical building blocks. Upon complex formation with Pd2+ at a 1:4 molar ratio, 1 and 1S initially form mononuclear PdL4 complexes (Pd2+ (1)4 and Pd2+ (1S )4 ) without formation of a cage. The PdL4 complexes undergo a stoichiometrically controlled structural transition to Pd2 L4 open cages ((Pd2+ )2 (1)4 and (Pd2+ )2 (1S )4 ) capable of anion binding, leading to turn-on anion binding. The structural transitions between the Pd2 L4 open cage and the PdL4 complex are reversible. Thus, stoichiometric addition (2 equiv) of free 1S to the (Pd2+ )2 (1S )4 open cage holding a guest anion ((Pd2+ )2 (1S )4 ⋅G- ) enables the structural transition to the Pd2+ (1S )4 complex, which does not have a cage and thus causes the release of the guest anion (Pd2+ (1S )4 +G- ).

This work revealed that significant asymmetric nonlinear effects can be found in a coordination-directed conformational alteration through competing allosteric mechanisms. Toward this aim, we have prepared new chiral bridging ligands [( S, S)- and ( R, R)-Im2An] containing an anthracene ring as a spacer with two ethynyl-linked chiral imidazole groups at the 9,10-positions. The ( S, S)- and ( R, R)-Im2An ligands (L) spontaneously form the assemblies with Zn2+ ions (M) in solution phase, giving L4M2-type assemblies with a general formula [( S, S)- or ( R, R)-Im2An]4(Zn2+)2. NMR studies revealed that the [( S, S)-Im2An]4(Zn2+)2 assembly has an anthracene dimer structure with a parallel-displaced geometry, leading to relatively small circular dichroism (CD) signals, as expected for nonchiral objects. Conversely, subsequent addition of chiral coligands [( R)- or ( S)-Ph-box] to [( S, S)-Im2An]4(Zn2+)2 afforded an alternative Zn2+ assembly with general formula [( R)- or ( S)-Ph-box]2[( S, S)-Im2An]2(Zn2+)2, where the chiral coligands expel two of the ( S, S)-Im2An ligands that were singly bound to the Zn2+ ions in the original [( S, S)-Im2An]4(Zn2+)2 assembly. This ligand-exchange reaction causes conformational alteration from a parallel-displaced structure to a twisted stacking between the anthracene rings inside the Zn2+ assembly, which results in a significant enhancement of CD signals due to excitonic interactions of the chiral anthracene dimer. Dissymmetry factor ( gCD) for CD due to chiral stacking structures shows a significant inverse sigmoidal response to the enantiomeric excess of the chiral coligands. The observed nonlinear phenomena are results of the two conflicting mechanisms, homochiral cooperative association (homochiral self-sorting) to form CD-active assemblies [( S)- or ( R)-Ph-box]2[( S, S)-Im2An]2(Zn2+)2 versus heterochiral cooperative dissociation of [( S, S)-Im2An]4(Zn2+)2 by sequestering of Zn2+ inside the assembly through formation of a heterochiral 2:1 Zn2+ complex ([( R)-Ph-box][( S)-Ph-box]Zn2+). The presented mechanisms provide a new strategy for generating switch-like OFF/ON states in chiral systems.

Monodentate ligand binding is facilitated by supramolecular chirality transformations from propeller-shaped chirality into single-twist chirality by altering the self-assembly of

A series of [5]carbohelicene derivatives substituted by electron-withdrawing maleimide and electron-donating methoxy, such as maleimide-substituted [5]carbohelicene (HeliIm) and methoxy-substituted HeliIm (MeO-HeliIm), were newly designed and synthesized to examine the electrochemical properties, excited-state dynamic and circularly polarized luminescence (CPL). First, electrochemical measurements and DFT calculations of [5]carbohelicene derivatives were performed by comparing with the structural isomers: picene derivatives. Introduction of an electron-withdrawing maleimide group onto a [5]carbohelicene core contributes to the stabilized LUMO state in HeliIm as compared to that of [5]carbohelicene (Heli), whereas the energy level of HOMO state in MeO-HeliIm increases by introducing electron-donating methoxy (MeO) groups onto a HeliIm skeleton. The HOMO–LUMO gap of MeO-HeliIm is smaller than those of HeliIm and Heli, which is similar to the steady-state spectroscopic measurements. The absolute fluorescence...

Tetrasulfone[9]helicene (PTSH) was newly synthesized to improve and evaluate its fluorescence and excited-state dynamics through a single-step oxidation reaction of tetrathia[9]helicene (PTTH). In electrochemical measurements, the reduction potential of PTSH was shifted in a positive direction by approximately 1.0 V when compared to that of PTTH because of its electron-accepting sulfone units. The results of the electrochemical measurements agree with the energy levels calculated by density functional theory (DFT) methods and steady-state spectroscopic measurements. Furthermore, a significant enhancement of the absolute fluorescence quantum yield (ΦFL) was achieved. The absolute fluorescence quantum yield of PTSH attained 0.27, which is approximately 10 times larger than that of PTTH (ΦFL = 0.03). Such an enhancement of ΦFL can be successfully explained by the corresponding kinetic comparison. The reason is mainly the increased energy gap ΔEST between the lowest singlet (S1) and triplet (T1) excited state...

A series of fluorescent "push-pull" tetrathia[9]helicenes based on quinoxaline (acceptor) fused with tetrathia[9]helicene (donor) derivatives was synthesized for control of the excited-state dynamics and circularly polarized luminescence (CPL) properties. In this work, introduction of a quinoxaline onto the tetrathia[9]helicene skeleton induced the "push-pull" character, which was enhanced by further introduction of an electron-releasing Me2 N group or an electron-withdrawing NC group onto the quinoxaline unit (denoted as Me2 N-QTTH and NC-QTTH, respectively). These trends were successfully discussed in terms of by electrochemical measurements and density functional theory (DFT) calculations. As a consequence, significant enhancements in the fluorescence quantum yields (ΦFL ) were achieved. In particular, the maximum ΦFL of Me2 N-QTTH was 0.43 in benzene (NC-QTTH: ΦFL =0.30), which is more than 20 times larger than that of a pristine tetrathia[9]helicene (denoted as TTH; ΦFL =0.02). These enhancements were also explained by kinetic discussion of the excited-state dynamics such as fluorescence and intersystem crossing (ISC) pathways. Such significant enhancements of the ΦFL values thus enabled us to show the excellent CPL properties. The value of anisotropy factor gCPL (normalized difference in emission of right-handed and left-handed circularly polarized light) was estimated to be 3.0 × 10(-3) for NC-QTTH.

Benzimidazole-fused [5]carbohelicene ([5]HeliBI) was newly synthesized to examine the spectroscopic and chiroptical properties. The reversible protonation and deprotonation processes of [5]HeliBI were successfully investigated using (1)H NMR, absorption and fluorescence spectral measurements. We also confirmed the circularly polarized luminescence of protonated [5]HeliBI (H(+)-[5]HeliBI). This is the first observation of red-coloured CPL of a helicene derivative.

A bisanthra-thianthrene has been synthesized and the oxidation property was studied to show that the bis(tetracene radical cation) linked by a dithiin ring is more stable than the π-expanded dithianonacene dication.

This work demonstrated that the ligand symmetry of europium(III) complexes controls the ratiometric luminescence characteristics of lanthanides. Nona-coordinated europium(III) complexes having unsymmetrical β-diketonate ligands (Cs) exhibit distinctive ratiometric spectral variations in the extremely narrow f–f transition bands over the temperature range from 253 to 323 K. In contrast, no such ratiometric change can be observed in a series of nona-coordinated europium(III) complexes containing symmetrical β-diketonate ligands (C2v). The remarkable difference depending on the ligand symmetry (Csvs. C2v) suggests that the coordination rearrangement of β-diketonate in the complex causes ratiometric spectral variations in extremely narrow f–f transition bands, where two europium(III) complex isomers exist in the solution equilibrium. A self-calibration method using dual iso-emissive points is reported, where self-calibration using the two emission intensities at the iso-emissive points reduces the coefficient of variation in luminescence thermometry.

Chiroptical photoswitches are of interest from a viewpoint of applications in advanced information technologies. We report dynamic on–off photoswitching of circularly polarized luminescence (CPL) in a binuclear europium complex system. Two coordination units are arranged closely in a chiral fashion by a photoresponsive ligand with a one-handed helical structure. The chirality in the helical scaffold is hierarchically transferred to the chirality in nine-coordinate complex sites. The chiral close arrangement of complex units induces the enrichment of a specific chiral coordination structure in the nine-coordinate europium sites. The chiral arrangement of complex units is switched in conjunction with the photoinduced helix–nonhelix structural change in the photoresponsive framework, demonstrating on–off switching of CPL with high contrast.

This work demonstrates that ligand-to-ligand interactions between achiral bis-β-diketonate (BTP) and chiral bis(4-phenyl-2-oxazolinyl)pyridine [( R)- or ( S)-Ph-Pybox] are successfully directed to the fabrication of a D

Heteroleptic zinc(II) complexes synthesized using achiral dipyrrinato and chiral bis(oxazoline) ligands show bright fluorescence with quantum efficiencies of up to 0.70. The fluorescence originates from the (1)π-π* photoexcited state localized exclusively on the dipyrrinato ligand. Furthermore, the luminescence is circularly polarized despite the achirality of the dipyrrinato ligand. Single-crystal X-ray structure analysis discloses that the chiral bis(oxazoline) ligand undergoes intramolecular π-π stacking with the dipyrrinato ligand, inducing axial chirality in the dipyrrinato moiety.

Directing the supramolecular polymerization towards a preferred type of organization is extremely important in the design of functional soft materials. Proposed herein is a simple methodology to tune the length and optical chirality of supramolecular polymers formed from a chiral bichromophoric binaphthalene by the control of enantiomeric excess (ee). The enantiopure compound gave thin fibers longer than a few microns, while the racemic mixture favored the formation of nanoparticles. The thermodynamic study unveils that the heterochiral assembly gets preference over the homochiral assembly. The stronger heterochiral binding over homochiral one terminated the elongation of fibrous assembly, thus leading to a control over the length of fibers in the nonracemic mixtures. The supramolecular polymerization driven by π-π interactions highlights the effect of the geometry of a twisted π-core on this self-sorting assembly.

This work demonstrates a novel photoactivatable turn-on-type lanthanide(iii) luminescence. A β-diketone substrate having redox-active pyrrole moieties (LH2) undergoes efficient photo-oxygenation to afford the corresponding α-alkoxy diketone (LHOH) in the presence of lanthanide(iii) ions, which trigger bright europium(iii) red luminescence (PA-EuIII) turn-on, as well as activating the near-infrared luminescence (λem = 976 nm) of ytterbium(iii). A photo-patterning process for security imaging is successfully demonstrated.

Asymmetric arylation of secondary silanes catalyzed by a Pd-chiral phosphoramidite complex was developed for application to low-molecular-weight circularly polarized luminescence (CPL) materials. The asymmetric arylation provided a convenient, efficient synthetic method for a variety of chiral tertiary silanes (2–21), which were key intermediates for preparing the quaternary silicon center. A stepwise, one-pot procedure was used to transform the appropriate aryl iodide to the quaternary silane (22) with good yield and enantioselectivity. Among compounds synthesized in this work, four optically pure tertiary silanes (18–21) were selected to investigate the relationship between the structure and optical properties. Optically pure (S,S)-21 displayed the highest CPL emission with a high fluorescence quantum yield (glum: +0.008, ΦF: 0.42). This simple molecular design provides new strategies for developing small organic CPL dyes.

To examine the versatility of the trans-bisglycoconjugation architecture for 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (TFPP) derivative-based photodynamic therapy (PDT), 25 porphyrin derivat...

This work demonstrates a simple methodology to tune the chiroptical properties of chiral europium(iii) complexes by supramolecular polymerization. Helical aggregation of the cesium derivative has updated the highest luminescence dissymmetry factor to date leading to naked eye visualization of circular polarized luminescence using circularly polarized filters.

This work demonstrates dual emission "OFF-ON-OFF" switching at visible and UV wavelengths of a carbazole functionalized β-diketone (LH) by a simple change of a europium(III) ion (Eu(3+)) concentration in the submicromolar concentration range. In the presence of 0.25 equiv of Eu(3+) (5 μM), LH forms a luminescent 4:1 complex ([Eu(3+)(L(-))4](-)) exhibiting dual emission at 357 and 613 nm resulting from the local excitation of the carbazole ring and ligand-sensitized luminescence from the Eu(3+)-β-diketonate unit, respectively. The 4:1 complex begins to convert into a 2:1 complex ([Eu(3+)(L(-))2](+)) via a 3:1 complex [Eu(3+)(L(-))3] above a molar ratio ([Eu(3+)]/[LH]) of 0.25, which provides the opportunity for binding of solvent methanol molecules to the vacant site of the Eu(3+) ion in the complex ([Eu(3+)(L(-))2(MeOH)n](+)). The OH oscillators of coordinated methanol molecules facilitate the nonradiative pathway of the Eu(3+) emission; hence the emission at 613 nm almost disappears above the 0.50 equivalent of Eu(3+) (11 μM), while the UV emission at 357 nm remains mostly constant over the whole concentration range.

We prepared perylene dications 1(2+) and 2(2+) by using "capped" perylene derivatives, and for the first time, successfully obtained single crystals of a perylene dication 1(2+) that enabled us to perform its structural analysis. We realized that the substituted aryl groups on perylene control the positions of positive charges, thus the remaining electronic system satisfies Clar's sextet rule toward the highest number of localized sextets. Experimental and theoretical evidence proved that Clar's aromatic π-sextet rule could be applied even for the dicationic perylenes in a very simple way.

The fabrication of nanocrystals (NCs) composed of the cationic Au(I) complex was demonstrated by the reprecipitation method in which the colloidal solution of the NCs showed brilliant green phosphorescence with a quantum yield of 83% in n-hexane. Characterization of the prepared NCs was performed by transmission electron microscopy observation and elemental analysis with energy-dispersive X-ray spectroscopy. The obtained Au(I) NCs were particles of random shapes with a diameter of 200-400 nm. The selected-area electron diffraction and X-ray diffraction measurements showed the characteristic diffraction patterns attributable to the crystal structure of the bulk crystal of the Au(I) complex. A similar method was performed with a different counteranion, leading to a colloidal solution of the microcrystals (MCs) with brilliant yellow phosphorescence and a quantum yield of 26% in n-hexane. Luminescence patterning of the NCs and MCs was also achieved successfully by electrophoretic deposition onto an indium tin oxide (ITO)-coated glass substrate, resulting in characteristic luminescence patterns on the ITO substrates with relatively high photoluminescence quantum yields.

Fabrication of nanorods (NRs) composed of a cationic Au(I) complex was demonstrated by means of the solution-injection method. A colloidal solution of the NRs showed brilliant bluish green photoluminescence with a quantum yield as high as 58%. The NRs were found to be 100–400 nm in width and 3–5 μm in length by transmission electron microscopy observations. Pattern formation of the NRs was achieved successfully after a selective electrophoretic deposition onto an indium tin oxide coated glass substrate, which maintains a relatively high luminescence quantum yield.

Sterically congested tetraarylpyrenes exhibited emission in both solution and the solid state. The monocationic species of pyrene 1 could be isolated because of the reasonably protected system. The aromaticity of 1 relocates from the biphenyl part to the naphthalene unit upon two-electron oxidation.