Systematic Introduction of Aromatic Rings to Diphosphine Ligands for Emission Color Tuning of Dinuclear Copper(I) Iodide Complexes

We have newly synthesized two solution-stable luminescent dinuclear copper­(I) complexes, [Cu₂(μ-I)₂(dpppy)₂] (<b>Cu-py</b>) and [Cu₂(μ-I)₂(dpppyz)₂] (<b>Cu-pyz</b>), where dpppy = 2,3-bis­(diphenylphosphino)­pyridine and dpppyz = 2,3-bis­(diphenylphosphino)­pyrazine, using chelating diphosphine ligands composed of N-heteroaromatic rings. X-ray analysis clearly indicates that the molecular structures of <b>Cu-py</b> and <b>Cu-pyz</b> are almost identical with that of the parent complex, [Cu₂(μ-I)₂(dppb)₂] [<b>Cu-bz</b>; dppb = 2,3-bis­(diphenylphosphino)­benzene]. Complexes <b>Cu-py</b> and <b>Cu-pyz</b> exhibit luminescence [emission quantum yield (Φ_em) = 0.48 and 0.02, respectively] in the solid state at 298 K. A wide emission color tuning, from 497 to 638 nm (energy = 0.55 eV, with an emission color ranging from green to reddish-orange), was achieved in the solid state by the introduction of pyridinic N atoms into the bridging phenyl group between the two diphenylphosphine groups. Density functional theory calculations suggest that the emission could originate from the effective combination of the metal-to-ligand charge-transfer excited state with the halide-to-ligand charge-transfer excited state. Thus, the emission color change is due to stabilization of the π* levels of the central aryl group in the diphosphine ligand. Furthermore, these copper­(I) complexes exhibit thermally activated delayed fluorescence at 298 K because of the small singlet–triplet energy difference (Δ<i>E</i> = 523 and 564 cm^–1 for <b>Cu-py</b> and <b>Cu-pyz</b>, respectively). The stability of these complexes in chloroform, due to the rigid bonds between the diphosphine ligands and the Cu^I ions, enables the preparation of emissive poly­(methyl methacrylate) films by the solution-doping technique

Emission Tuning of Luminescent Copper(I) Complexes by Vapor-Induced Ligand Exchange Reactions

We have synthesized two luminescent mononuclear Cu­(I) complexes, [Cu­(PPh₂Tol)­(THF)­(4Mepy)₂]­(BF₄) (<b>1</b>) and [Cu­(PPh₂Tol)­(4Mepy)₃]­(BF₄) (<b>2</b>) (PPh₂Tol = diphenyl­(<i>o</i>-tolyl)­phosphine, 4Mepy = 4-methylpyridine, THF = tetrahydrofuran), and investigated their crystal structures, luminescence properties, and vapor-induced ligand exchange reactions in the solid state. Both coordination complexes are tetrahedral, but one of the three 4Mepy ligands of complex <b>2</b> is replaced by a THF solvent molecule in complex <b>1</b>. In contrast to the very weak blue emission of the THF-bound complex <b>1</b> (wavelength of emission maximum (λ_em) = 457 nm, emission quantum yield (Φ_em) = 0.02) in the solid state at room temperature, a very bright blue-green emission was observed for <b>2</b> (λ_em = 484 nm, Φ_em = 0.63), suggesting a contribution of the THF ligand to nonradiative deactivation. Time-dependent density functional theory calculations and emission lifetime measurements suggest that the room-temperature emissions of the complexes are due to thermally activated delayed fluorescence from the metal-to-ligand charge transfer excited state. Interestingly, by exposing the solid sample of THF-bound <b>1</b> to 4Mepy vapor, the emission intensity drastically increased and the emission color changed from blue to blue-green. Powder X-ray diffraction measurements revealed that the emission change of <b>1</b> is due to the vapor-induced ligand exchange of THF for 4Mepy, forming the strongly emissive complex <b>2</b>. Further emission tuning was achieved by exposing <b>1</b> to pyrimidine or pyrazine vapors, forming green (λ_em = 510 nm) or orange (λ_em = 618 nm) emissive complexes, respectively. These results suggest that the vapor-induced ligand exchange is a promising method to control the emission color of luminescent Cu­(I) complexes

Distal middle cerebral artery (MCA) pattern and infarct volume.

<p>(A) Distal MCA patterns were more complex in SP.MES (median 3, interquartile range [IQR] 3–5) than PM0/SHRSP (median 2, IQR 1–3) (Mann-Whitney u-test, p = 0.001). (B) Representative brain sections stained with 2,3,5-triphenyltetrazolium chloride (TTC) from PM0 subjected to distal middle cerebral artery occlusion (MCAO) 24 h earlier. (C) Infarct volume in the SP.MES group was 89±39 mm³, which was not significantly different from 83±35 mm³ in the PM0/SHRSP group. Infarct volume was linearly correlated with distal MCA branching pattern. (D) The adjusted mean of infarct volume was significantly smaller in SP.MES compared with that in PM0/SHRSP (67 [95% CI 46 to 87] mm³ vs. 100 [95% CI 82 to 118] mm³, p = 0.032). Data are expressed as mean±S.D.</p

Physiological variables in SP.MES and PM0/SHRSP.

<p>Values are mean±S.D.</p><p>*p = 0.006 vs. PM0/SHRSP, unpaired t-test.</p><p>Physiological variables in SP.MES and PM0/SHRSP.</p

Mean arterial blood pressure (MABP) and Cerebral blood flow (CBF).

<p>(A) Changes in MABP before and after distal MCA occlusion: 2-way ANOVA revealed a group difference and an effect of time (**p<0.001 and *p<0.05 vs. 0 min, #p<0.001 between the groups, Values are mean±S.D.). (B) 2-way ANOVA did not show a significant group difference in CBF after MCA occlusion. Data are expressed as mean±S.D.</p

Construction of congenic strains.

<p>The mutated <i>Cyba</i> allele of MES was introgressed onto the genomic background of SHRSP. Using the MES strain as the donor and SHRSP/Izm as the recipient, we constructed a congenic strain without p22phox protein with SHRSP/Izm background by the speed congenic strategy. The target region was between D19Rat21 and D19Rat105. After 5 generations of backcrossing, all the 140 background simple sequence repeat markers were confirmed to be homozygous for the recipient allele, and then the congenic strain with the target region homozygous for the donor strain (i.e., MES) was obtained through brother-sister matings (SP.MES). Rats with the target region homozygous for the recipient strain (i.e., SHRSP/Izm) were used as control (PM0). The congenic region was maximally 1.7-Mbp between the two markers. The box indicates the region from the MES rat, and the vertical bar shows the region containing the recombination break point.</p

Physiological variables in SHR/Izm (5–7 months old).

<p>Values are mean±S.D.</p><p>Physiological variables in SHR/Izm (5–7 months old).</p

Branching pattern of diatal MCA.

<p>(A) The branching pattern of distal middle cerebral artery (MCA) modified from Cai H et al. (<i>Stroke</i> 1998;29:1982–1987). (B)-(E) Examples of distal middle cerebral artery (MCA) pattern (B, Type 1; C, Type 3; D, Type 6; E, 2MCAs) are presented. (F)-(H) In 2 SP.MES rats, we found extremely atypical distal MCA (named as Type X). When the distal MCA was occluded in a routine manner (F), blood flow was maintained through an aberrant vessel (arrow). In the second case, however, we could block this aberrant blood flow (X) by placing the laser beam at 2 separate points (H). (I) Fenestration of distal MCA in a SP.MES rat. We excluded atypical distal MCAs (E-I, i.e., 2MCAs, Type X, and fenestration) from the analysis.</p

Retrospective analysis.

<p>(A) the frequency of distal MCA pattern in male spontaneously hypertensive rats (SHR),stroke-prone SHR (SHRSP), and Wistar-Kyoto rats (WKY). (B) infarct volume after distal MCA occlusion in SHR (5–7 months old, male) with simple (N = 16), regular (N = 25), or complicated (N = 8) MCA. *p = 0.017 vs. complicated, ANOVA & post-hoc Bonferroin test.</p

Vapochromic Luminescence and Flexibility Control of Porous Coordination Polymers by Substitution of Luminescent Multinuclear Cu(I) Cluster Nodes

Two luminescent porous coordination polymers (PCPs), i.e., [Cu₂(μ₂-I)₂ctpyz]_<i>n</i> and [Cu₄(μ₃-I)₄ctpyz]_<i>n</i> (<b>Cu2</b> and <b>Cu4</b>, respectively; ctpyz = <i>cis</i>-1,3,5-cyclohexanetriyl-2,2′,2″-tripyrazine), were successfully synthesized and characterized by single-crystal X-ray diffraction and luminescence spectroscopic measurements. <b>Cu2</b> consists of rhombus-type dinuclear {Cu₂I₂} cores bridged by ctpyz ligands, while <b>Cu4</b> is constructed of cubane-type tetranuclear {Cu₄I₄} cores bridged by ctpyz ligands. The void fraction of <b>Cu4</b> is estimated to be 48.0%, which is significantly larger than that of <b>Cu2</b> (19.9%). Under UV irradiation, both PCPs exhibit red luminescence at room temperature in the solid state (λ_em values of 660 and 614 nm for <b>Cu2</b> and <b>Cu4</b>, respectively). Although the phosphorescence of <b>Cu2</b> does not change upon removal and/or adsorption of EtOH solvent molecules in the porous channels, the solid-state emission maximum of <b>Cu4</b> red-shifts by 36 nm (λ_em = 650 nm) upon the removal of the adsorbed benzonitrile (PhCN) molecules from the porous channels (and vice versa). This large difference in the vapochromic behavior of <b>Cu2</b> and <b>Cu4</b> is closely related to the framework flexibility. The framework of <b>Cu2</b> is sufficiently rigid to retain the porous structure without solvated EtOH molecules, whereas the porous structure of <b>Cu4</b> collapses easily after removal of the adsorbed PhCN molecules to form a nonporous amorphous phase. The original vapor-adsorbed porous structure of <b>Cu4</b> is regenerated by exposure of the amorphous solid to not only PhCN vapor but also tetrahydrofuran, acetone, ethyl acetate, and <i>N</i>,<i>N</i>-dimethylformamide vapors. The <b>Cu4</b> structures with the various adsorbed solvents showed almost the same emission maxima as the original PhCN-adsorbed <b>Cu4</b>, except for DMF-adsorbed <b>Cu4</b>, which showed no luminescence probably because of weak coordination of the DMF vapor molecules to the Cu­(I) centers of the tetranuclear {Cu₄I₄} core