Fluorescence Properties of (<i>E</i>,<i>E</i>,<i>E</i>)‑1,6-Di(<i>n</i>‑naphthyl)-1,3,5-hexatriene (<i>n</i> = 1, 2): Effects of Internal Rotation

The fluorescence spectroscopic properties of (<i>E</i>,<i>E</i>,<i>E</i>)-1,6-di­(<i>n</i>-naphthyl)-1,3,5-hexatrienes (<b>1</b>, <i>n</i> = 1; <b>2</b>, <i>n</i> = 2) have been investigated in solution and in the solid state. In solution, the absorption maxima (λ_a) of the lowest-energy band (<b>1</b>, 374 nm; <b>2</b>, 376 nm in methylcyclohexane) were similar for <b>1</b> and <b>2</b>, whereas the fluorescence maxima (λ_f) (<b>1</b>, 545 nm; <b>2</b>, 453 nm) and quantum yields (ϕ_f) (<b>1</b>, 0.046; <b>2</b>, 0.68) were very different regardless of the solvent polarity. The fluorescence spectrum of <b>1</b> was independent of the excitation wavelength (λ_ex), whereas the spectrum of <b>2</b> was weakly λ_ex-dependent. In the solid state, the spectroscopic properties of <b>1</b> and <b>2</b> were similar (λ_a = 437–438 nm, λ_f = 496–505 nm, ϕ_f = 0.04–0.07). The origins of emission are both considered to be mainly monomeric. With the help of single-crystal X-ray structure analysis and ab initio quantum chemical calculation, we conclude that the red-shifted and weak emission of <b>1</b> in solution originates from a planar excited state having small charge transfer character, reached from a twisted Franck–Condon state by the excited-state geometrical relaxation accompanied by the internal rotation around the naphthalene (Ar)–CH single bond. The similar fluorescence properties of <b>1</b> and <b>2</b> in the solid state can be attributed to the restriction of the geometrical relaxation. The effects of the Ar–CH rotational isomerism on the fluorescence properties in solution, for <b>2</b> in particular, are also discussed

Fluorescence Properties of (<i>E</i>,<i>E</i>,<i>E</i>)‑1,6-Di(<i>n</i>‑naphthyl)-1,3,5-hexatriene (<i>n</i> = 1, 2): Effects of Internal Rotation

The fluorescence spectroscopic properties of (<i>E</i>,<i>E</i>,<i>E</i>)-1,6-di­(<i>n</i>-naphthyl)-1,3,5-hexatrienes (<b>1</b>, <i>n</i> = 1; <b>2</b>, <i>n</i> = 2) have been investigated in solution and in the solid state. In solution, the absorption maxima (λ_a) of the lowest-energy band (<b>1</b>, 374 nm; <b>2</b>, 376 nm in methylcyclohexane) were similar for <b>1</b> and <b>2</b>, whereas the fluorescence maxima (λ_f) (<b>1</b>, 545 nm; <b>2</b>, 453 nm) and quantum yields (ϕ_f) (<b>1</b>, 0.046; <b>2</b>, 0.68) were very different regardless of the solvent polarity. The fluorescence spectrum of <b>1</b> was independent of the excitation wavelength (λ_ex), whereas the spectrum of <b>2</b> was weakly λ_ex-dependent. In the solid state, the spectroscopic properties of <b>1</b> and <b>2</b> were similar (λ_a = 437–438 nm, λ_f = 496–505 nm, ϕ_f = 0.04–0.07). The origins of emission are both considered to be mainly monomeric. With the help of single-crystal X-ray structure analysis and ab initio quantum chemical calculation, we conclude that the red-shifted and weak emission of <b>1</b> in solution originates from a planar excited state having small charge transfer character, reached from a twisted Franck–Condon state by the excited-state geometrical relaxation accompanied by the internal rotation around the naphthalene (Ar)–CH single bond. The similar fluorescence properties of <b>1</b> and <b>2</b> in the solid state can be attributed to the restriction of the geometrical relaxation. The effects of the Ar–CH rotational isomerism on the fluorescence properties in solution, for <b>2</b> in particular, are also discussed

Diamondoid Porous Organic Salts toward Applicable Strategy for Construction of Versatile Porous Structures

To achieve efficient construction of organic porous materials with versatile properties, we propose a widely applicable novel strategy using organic salts comprising triphenylmethylamine (TPMA) and sulfonic acids. We demonstrate that TPMA and sulfonic acids having polyaromatic moieties give a new class of porous structures consisting of diamond networks, named as diamondoid porous organic salts (<i>d</i>-POSs). In the <i>d</i>-POSs, TPMA and the sulfonic acids are assembled into stable tetrahedral supramolecular clusters via charge-assisted hydrogen bonding as primary building blocks. Subsequently, the clusters are accumulated by π–π interactions between the polyaromatic moieties to yield the <i>d</i>-POSs through formation of the diamond networks. Large steric hindrance of the clusters prevents the diamond networks from constructing highly interpenetrated structures, giving continuous open channels. It should be noted that the interpenetration degree of the diamond networks is controlled by tuning the bulkiness of the cluster with alteration of sulfonic acids. Anthracene-2-sulfonic acid (2-AS) constructs a 3-fold structure with one-dimensional channels, whereas pyrene-1-sulfonic acid (1-PyS) yields a 2-fold structure having two-dimensional channels. Furthermore, the organic salt of TPMA and 2-AS also give polymorphic structures in response to host–guest ratio and guest species, indicating not only their stability but the flexibility of the <i>d</i>-POSs

Elucidation of Anthracene Arrangement for Excimer Emission at Ambient Conditions

Solid-state excimer emission of anthracene and its derivatives is a rare case at ambient conditions. We have designed organic salts composed of 9,10-bis­(4-aminophenyl)­anthracene (BAPA) and mineral acids in order to regulate the anthracene arrangement for investigation of the plausible geometry. From fluorescence measurement of three BAPA salts (nitrate: salt 1, chloride: salt 2, phosphate: salt 3), emission colors were changed by the effect of the mineral acids on the crystal structure. Notably, salt 3 crystal exhibited a bluish-green color derived from excimer emission at ambient conditions. On the basis of X-ray crystallographic analysis, the excimer emission of the salt 3 crystal was attributed to a tilt–slide type of anthracene geometry. In the geometry, π-planes of the anthracene moieties partially overlapped next to each other, an angle between the π-planes is 44°, and the nearest C–C distance is 3.7 Å. Such molecular geometry of partial overlapping of the anthracene rings and slightly longer C–C distance than that of common active π–π interaction (3.4–3.5 Å) was constructed of OH···O hydrogen bonds among mineral acid ions. These results suggest that the hydrogen bonds among mineral acid ions lead to the proximity of BAPA, following the excimer emission

Diamondoid Porous Organic Salts toward Applicable Strategy for Construction of Versatile Porous Structures

To achieve efficient construction of organic porous materials with versatile properties, we propose a widely applicable novel strategy using organic salts comprising triphenylmethylamine (TPMA) and sulfonic acids. We demonstrate that TPMA and sulfonic acids having polyaromatic moieties give a new class of porous structures consisting of diamond networks, named as diamondoid porous organic salts (<i>d</i>-POSs). In the <i>d</i>-POSs, TPMA and the sulfonic acids are assembled into stable tetrahedral supramolecular clusters via charge-assisted hydrogen bonding as primary building blocks. Subsequently, the clusters are accumulated by π–π interactions between the polyaromatic moieties to yield the <i>d</i>-POSs through formation of the diamond networks. Large steric hindrance of the clusters prevents the diamond networks from constructing highly interpenetrated structures, giving continuous open channels. It should be noted that the interpenetration degree of the diamond networks is controlled by tuning the bulkiness of the cluster with alteration of sulfonic acids. Anthracene-2-sulfonic acid (2-AS) constructs a 3-fold structure with one-dimensional channels, whereas pyrene-1-sulfonic acid (1-PyS) yields a 2-fold structure having two-dimensional channels. Furthermore, the organic salt of TPMA and 2-AS also give polymorphic structures in response to host–guest ratio and guest species, indicating not only their stability but the flexibility of the <i>d</i>-POSs

Diamondoid Porous Organic Salts toward Applicable Strategy for Construction of Versatile Porous Structures

To achieve efficient construction of organic porous materials with versatile properties, we propose a widely applicable novel strategy using organic salts comprising triphenylmethylamine (TPMA) and sulfonic acids. We demonstrate that TPMA and sulfonic acids having polyaromatic moieties give a new class of porous structures consisting of diamond networks, named as diamondoid porous organic salts (<i>d</i>-POSs). In the <i>d</i>-POSs, TPMA and the sulfonic acids are assembled into stable tetrahedral supramolecular clusters via charge-assisted hydrogen bonding as primary building blocks. Subsequently, the clusters are accumulated by π–π interactions between the polyaromatic moieties to yield the <i>d</i>-POSs through formation of the diamond networks. Large steric hindrance of the clusters prevents the diamond networks from constructing highly interpenetrated structures, giving continuous open channels. It should be noted that the interpenetration degree of the diamond networks is controlled by tuning the bulkiness of the cluster with alteration of sulfonic acids. Anthracene-2-sulfonic acid (2-AS) constructs a 3-fold structure with one-dimensional channels, whereas pyrene-1-sulfonic acid (1-PyS) yields a 2-fold structure having two-dimensional channels. Furthermore, the organic salt of TPMA and 2-AS also give polymorphic structures in response to host–guest ratio and guest species, indicating not only their stability but the flexibility of the <i>d</i>-POSs

Exclusive Formation of Bridge-Substituted [2.2]Paracyclophane by Topochemical Photocycloaddition Reaction of Unsymmetrical Substituted <i>p</i>‑Quinodimethane

Unsymmetrical 7-(2′-bromoethoxycarbonyl)-7,8,8-tris­(methoxycarbonyl)-<i>p</i>-quinodimethane (<b>2</b>) underwent a quantitative intermolecular [6 + 6] photocycloaddition reaction through a single crystal-to-single crystal transformation to afford a bridge-substituted [2.2]­paracyclophane (<b>3</b>). The crystal structure of <b>2</b> indicates that the bromoethoxy groups conveniently form σ-halogen bonds with the carboxyl groups to yield 2-fold helical assemblies of an isolated pair of <b>2</b>. <b>3</b> has a relatively long distance between bridged carbon–carbon bonds in comparison with the known ones. Such bonds caused an one-side insertion reaction of molecular oxygen in solution to afford the peroxide bridge-substituted [2.2]­paracyclophane in a quantitative yield

Diamondoid Porous Organic Salts toward Applicable Strategy for Construction of Versatile Porous Structures

To achieve efficient construction of organic porous materials with versatile properties, we propose a widely applicable novel strategy using organic salts comprising triphenylmethylamine (TPMA) and sulfonic acids. We demonstrate that TPMA and sulfonic acids having polyaromatic moieties give a new class of porous structures consisting of diamond networks, named as diamondoid porous organic salts (<i>d</i>-POSs). In the <i>d</i>-POSs, TPMA and the sulfonic acids are assembled into stable tetrahedral supramolecular clusters via charge-assisted hydrogen bonding as primary building blocks. Subsequently, the clusters are accumulated by π–π interactions between the polyaromatic moieties to yield the <i>d</i>-POSs through formation of the diamond networks. Large steric hindrance of the clusters prevents the diamond networks from constructing highly interpenetrated structures, giving continuous open channels. It should be noted that the interpenetration degree of the diamond networks is controlled by tuning the bulkiness of the cluster with alteration of sulfonic acids. Anthracene-2-sulfonic acid (2-AS) constructs a 3-fold structure with one-dimensional channels, whereas pyrene-1-sulfonic acid (1-PyS) yields a 2-fold structure having two-dimensional channels. Furthermore, the organic salt of TPMA and 2-AS also give polymorphic structures in response to host–guest ratio and guest species, indicating not only their stability but the flexibility of the <i>d</i>-POSs

Elucidation of Anthracene Arrangement for Excimer Emission at Ambient Conditions

Solid-state excimer emission of anthracene and its derivatives is a rare case at ambient conditions. We have designed organic salts composed of 9,10-bis­(4-aminophenyl)­anthracene (BAPA) and mineral acids in order to regulate the anthracene arrangement for investigation of the plausible geometry. From fluorescence measurement of three BAPA salts (nitrate: salt 1, chloride: salt 2, phosphate: salt 3), emission colors were changed by the effect of the mineral acids on the crystal structure. Notably, salt 3 crystal exhibited a bluish-green color derived from excimer emission at ambient conditions. On the basis of X-ray crystallographic analysis, the excimer emission of the salt 3 crystal was attributed to a tilt–slide type of anthracene geometry. In the geometry, π-planes of the anthracene moieties partially overlapped next to each other, an angle between the π-planes is 44°, and the nearest C–C distance is 3.7 Å. Such molecular geometry of partial overlapping of the anthracene rings and slightly longer C–C distance than that of common active π–π interaction (3.4–3.5 Å) was constructed of OH···O hydrogen bonds among mineral acid ions. These results suggest that the hydrogen bonds among mineral acid ions lead to the proximity of BAPA, following the excimer emission

Diamondoid Porous Organic Salts toward Applicable Strategy for Construction of Versatile Porous Structures

To achieve efficient construction of organic porous materials with versatile properties, we propose a widely applicable novel strategy using organic salts comprising triphenylmethylamine (TPMA) and sulfonic acids. We demonstrate that TPMA and sulfonic acids having polyaromatic moieties give a new class of porous structures consisting of diamond networks, named as diamondoid porous organic salts (<i>d</i>-POSs). In the <i>d</i>-POSs, TPMA and the sulfonic acids are assembled into stable tetrahedral supramolecular clusters via charge-assisted hydrogen bonding as primary building blocks. Subsequently, the clusters are accumulated by π–π interactions between the polyaromatic moieties to yield the <i>d</i>-POSs through formation of the diamond networks. Large steric hindrance of the clusters prevents the diamond networks from constructing highly interpenetrated structures, giving continuous open channels. It should be noted that the interpenetration degree of the diamond networks is controlled by tuning the bulkiness of the cluster with alteration of sulfonic acids. Anthracene-2-sulfonic acid (2-AS) constructs a 3-fold structure with one-dimensional channels, whereas pyrene-1-sulfonic acid (1-PyS) yields a 2-fold structure having two-dimensional channels. Furthermore, the organic salt of TPMA and 2-AS also give polymorphic structures in response to host–guest ratio and guest species, indicating not only their stability but the flexibility of the <i>d</i>-POSs