Two-photon absorption in three-dimensional chromophores based on [2.2]-paracyclophane

A series of alpha,omega-bis donor substituted oligophenylenevinylene dimers held together by the [2.2]paracyclophane core were synthesized to probe how the number of repeat units and through-space delocalization influence two-photon absorption cross sections. Specifically, the paracyclophane molecules are tetra(4,7,12,15)-(4'-dihexylaminostyryl)[2.2]paracyclophane (3R(D)), tetra(4,7,12,15)-(4' '-(4'-dihexylaminostyryl)styryl)[2.2]paracyclophane (5R(D)), and tetra(4,7,12,15)-(4' "-(4' '-(4'-dihexylaminostyryl)styryl)styryl)[2.2]paracyclophane (7R(D)). The compounds bis(1,4)-(4'-dihexylaminostyryl)benzene (3R) and bis(1,4)-(4' '-(4'-dihexylaminostyryl)styryl)benzene (5R) were also synthesized to reveal the properties of the "monomeric" counterparts. The two-photon absorption cross sections were determined by the two-photon induced fluorescence method using both femtosecond and nanosecond pulsed lasers as excitation sources. While there is a red shift in the linear absorption spectra when going from the "monomer" chromophore to the paracyclophane "dimer" (i.e., 3R --> 3R(D), 5R --> 5R(D)), there is no shift in the two-photon absorption maxima. A theoretical treatment of these trends and the dependence of transition dipole moments on molecular structure rely on calculations that interfaced time-dependent density functional theory (TDDFT) techniques with the collective electronic oscillator (CEO) program. These theoretical and experimental results indicate that intermolecular interactions can strongly affect B(u) states but weakly perturb A(g) states, due to the small dipole-dipole coupling between A(g) states on the chromophores in the dimer.     

Stereoselective synthesis of homoallylic alcohols of the [2.2]paracyclophane series and their use as auxiliaries in asymmetric allylboration of aldehydes

Stereoselectivity of allylboration of 4-formyl[2.2]paracyclophane, 4-acetyl[2.2]paracyclophane, and 4-hydroxy-5-formyl[2.2]paracyclophane was studied and the relative configurations of the homoallylic alcohols obtained were established. Optically pure (Sp,Sc)-(+)-4-(4-hydroxy-1-methylbut-3-enyl)[2.2]paracyclophane and (Rc,Sc)-(+)-4-hydroxy-5-(4-hydroxybut-3-enyl)[2.2]paracyclophane were synthesized. The possibility of using (Sp,Sc)-(+)-4-(4-hydroxy-4-methylbut-3-enyl)[2.2]paracyclophane as a recoverable chiral auxiliary in asymmetric allylboration of aldehydes was demonstrated. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 914–921, May, 2000.     

The phane properties of anti-[2.2](1,4)biphenylenophane

[structure: see text] Anti-[2.2](1,4)biphenylenophane (4) was synthesized from de Meijere's tetrabromo[2.2]paracyclophane (5) through a four-step reaction sequence. Although an average separation of 3.09 A between the inner ring of the biphenylene units is normal for [2.2]paracyclophanes, a bond distance of 1.54 Afor the ethano C-C bridge at room temperature is shorter than usual. In addition, trimethylsilyl-substituted anti-[2.2](1,4)biphenylenophane 8 sublimes at 220 degrees C under a pressure lower than 1 x10(-5) Torr without decomposition or thermal isomerization. The high thermal stability of 8 suggested that the ethano bridges of the biphenylenophanes are less strained than those of [2.2]paracyclophane. Bathochromic shifts are observed in their UV-vis absorption spectra. The phane state interactions of 4 and 8 were evidenced by the weak structureless fluorescent emission maximized at 537 and 550 nm in CH(2)Cl(2) along with longer relaxation lifetimes of 229 and 292 ps, respectively.     

Water-soluble [2.2]paracyclophane chromophores with large two-photon action cross sections

A series of alpha,omega-donor-substituted distyrylbenzene dimers held together by the [2.2]paracyclophane core were designed, synthesized, and characterized. Different substituents were chosen to modulate the strength of the donor nitrogen groups and to allow the molecules to be either neutral and soluble in nonpolar organic solvents or charged and water-soluble. The specific neutral structures are (in order of decreasing donor strength) 4,7,12,15-tetra[N,N-bis(6' '-chlorohexyl)-4'-aminostyryl]-[2.2]paracyclophane (1N), 4,7,12,15-tetra[(N-(6' '-chlorohexyl)carbazol-3'-yl)vinyl]-[2.2]paracyclophane (2N), and 4,7,12,15-tetra[N,N-bis(4' '-(6' '-chlorohexyl)phenyl)-4'-aminostyryl]-[2.2]paracyclophane (3N). The charged species are 4,7,12,15-tetra[N,N-bis(6' '-(N,N,N-trimethylammonium)hexyl)-4'-aminostyryl]-[2.2]paracyclophane octaiodide (1C), 4,7,12,15-tetra[(N-(6' '-(N,N,N-trimethylammonium)hexyl)carbazol-3'-yl)vinyl]-[2.2]paracyclophane octaiodide (2C), and 4,7,12,15-tetra[N,N-bis(4' '-(6' '-(N,N,N-trimethylammonium)hexyl)phenyl)-4'-aminostyryl]-[2.2]paracyclophane octaiodide (3C). Two-photon excitation spectra, measured using the two-photon induced fluorescence technique, show in toluene the following trend for the two-photon cross sections (delta): 3N > 2N > 1N. In water the delta values follow the same order, 3C approximately 2C > 1C, but are smaller (approximately one-third). Significantly, the fluorescence quantum yield (eta) in water decreases much more for 1, relative to 2 and 3. The two-photon action cross sections (deltaeta) of 2C and 3C are 294 GM and 359 GM, respectively. These values are among the highest reported thus far. These results show that, to maximize the deltaeta in this class of chromophores, one needs to fine-tune the magnitude of the charge transfer character of the excited state, to minimize fluorescence quenching in polar media.     

Synthesis of perfluoro[2.2]paracyclophane

A synthesis of perfluoro[2.2]paracyclophane has been sought ever since the partially fluorinated octafluoro[2.2]paracyclophane (AF4) was prepared and its chemistry studied. This compound has now been prepared in 39% yield from the precursor, 1,4-bis(chlorodifluoromethyl)-2,3,5,6-tetrafluorobenzene by its reaction with Zn when heated in acetonitrile at 100 degrees C. Two preparations of the precursor, first from 1,4-dicyano-2,3,5,6-tetrachlorobenzene and an improved method beginning from 1,2,4,5-tetrachlorobenzene, are also described as are key comparisons to our related synthesis of AF4.     

14][14]Metaparacyclophane: first example of an [m][n]metaparacyclophane

The synthesis of [14][14]metaparacyclophane, the first [m][n]metaparacyclophane ever known, is described. The reaction sequence began with the bis-chloromethylation of [14]paracyclophane in refluxing CS(2), which yielded a nonseparable mixture of 16,19- and 16,20-bis(chloromethyl)[14]paracyclophane in an 8:1 ratio. Acetolysis of these dichlorides gave the corresponding diacetate mixture from which the minor component 16,20-bis(acetoxymethyl)[14]paracyclophane was isolated and elaborated into the desired cyclophane via the disulfone of 2,15-dithia[16][14]metaparacyclophane and subsequent sulfur dioxide extrusion by a one-flask Ramberg-B?cklund reaction procedure followed by hydrogenation.     

New phosphorescent polynuclear Cu(I) compounds based on linear and star-shaped 2-(2'-pyridyl)benzimidazolyl derivatives: syntheses, structures, luminescence, and electroluminescence

Four dinuclear and trinuclear Cu(I) complexes that contain 2-(2'-pyridyl)benzimidazolyl derivative ligands including 1,4-bis[2-(2'-pyridyl)benzimidazolyl]benzene (1,4-bmb), 1,3-bis[2-(2'-pyridyl)benzimidazolyl]benzene (1,3-bmb), 1,3,5-tris[2-(2'-pyridyl)benzimidazolyl]benzene (tmb), and 4,4'-bis[2-(2'-pyridyl)benzimidazolyl]biphenyl (bmbp) have been synthesized. The formulas of these complexes are [Cu(2)(1,4-bmb)(PPh(3))(4)][BF(4)](2) (1), [Cu(2)(1,3-bmb)(PPh(3))(4)][BF(4)](2) (2), [Cu(3)(tmb)(PPh(3))(6)][BF(4)](3) (3), and [Cu(2)(bmbp)(PPh(3))(4)][BF(4)](2) (4), respectively. The crystal structures of 2-4 have been determined by single-crystal X-ray diffraction analyses. The Cu(I) ions in the complexes have a distorted tetrahedral geometry. For 3, two structural isomers (syn and anti) resulted from two different orientations of the three 2-(2'-pyridyl)benzimidazolyl chelating units were observed in the crystal lattice. Variable-temperature (1)H NMR experiments established the presence of syn and anti isomers for 1-3 in solution which interconvert at ambient temperature. Complexes 1-4 have a weak MLCT absorption band in the 350-450 nm region and display a yellow-orange emission when irradiated by UV light. One unexpected finding is that the yellow-orange emission of complexes 1-4 has a very long decay lifetime (approximately 200 micros) at 77 K. An electroluminescent (EL) device using 4 as the emitter and PVK as the host was fabricated. However, the long decay lifetime of the copper complexes may limit their applications as phosphorescent emitters in EL devices.     

The 4,4'-(1,2-ethanediyl)bisbenzyl biradical: its generation, detection, and (photo)chemical behavior in solution

The 4,4'-(1,2-ethanediyl)bisbenzyl biradical (2) is clearly and efficiently generated by photolysis of [3.2]paracyclophane-2-one (8) in cyclohexane solution. This intermediate is also formed via two-photon processes from [2.2]paracyclophane (3) and 1,2-bis(4-chloromethylphenyl)ethane (4). The products arising thermally from biradical 2 are [2.2]paracyclophane and [2.2.2.2]paracyclophane (11) (under high-intensity conditions). Furthermore, two-laser two-color flash photolysis shows that biradical 2 is photostable in solution at room temperature. Thus, formation of p-xylylene (1) from 2 occurs neither thermally nor photochemically.     

Blue luminescent 2-(2'-pyridyl)benzimidazole derivative ligands and their orange luminescent mononuclear and polynuclear organoplatinum(II) complexes

Five new 2-(2'-pyridyl)benzimidazole derivative ligands, 1,4-bis[2-(2'-pyridyl)benzimidazolyl]benzene (1,4-bmb), 4,4'-bis[2-(2'-pyridyl)benzimidazolyl]biphenyl (bmbp), 1-bromo-4-[2-(2'-pyridyl)benzimidazolyl]benzene (Brmb), 1,3-bis[2-(2'-pyridyl)benzimidazolyl]benzene (1,3-bmb), and 1,3,5-tris[2-(2'-pyridyl)benzimidazolyl]benzene (tmb), have been synthesized by Ullmann condensation methods. The corresponding mononuclear and polynuclear PtII complexes, Pt2(1,4-bmb)Ph4 (1), Pt2(bmbp)Ph4 (2), Pt(Brmb)Ph2 (3), Pt2(1,3-bmb)Ph4 (4), and Pt3(tmb)Ph6 (5), have been obtained by the reaction of the appropriate ligand with [PtPh2(SMe2)]n. The structures of the free ligands 1,4-bmb, bmbp, and tmb, as well as the complexes 1-3, were determined by single-crystal X-ray diffraction. All ligands display fluorescent emissions in the purple/blue region of the spectrum at ambient temperature and phosphorescent emissions in the blue/green region at 77 K, which are attributable to ligand-centered pi --> pi* transition. No ligand-based emission was observed for the PtII complexes 1-5. All PtII complexes display orange/red emissions at 77 K in a frozen solution or in the solid state, attributable to metal-to-ligand charge transfers (MLCT). Variable-temperature 1H NMR experiments establish that complexes 1, 4, and 5 exist in isomeric forms in solution at ambient temperature due to the hindered rotation of the square PtC2N2 planes in the complexes.     

Kinetic stabilization of the [1.1]paracyclophane system: isolation and X-ray structural analysis of a [1.1]paracyclophane derivative and its interconversion with the transannular adduct

Intentionally designed kinetic stabilization of the [1.1]paracyclophane skeleton has been achieved by multiple substitution of the aromatic rings with trimethylsilylmethyl and N,N-dimethyl-carbamoyl groups, which serve to shield the proximate bridgehead carbon atoms sterically from access by other reagents. The bis(Dewar benzene) precursor (1a) has been prepared in essentially the same manner as previous derivatives--starting from the photocycloaddition of 1,4-bis(trimethylsilyl)-2-butyne to octa-hydroindacene-1,5-dione--except for a few critical modifications described in the text. Substituted [1.1]paracyclophane (2a), photochemically generated from the precursor, is indefinitely stable at 50 degrees C and suffers decomposition only by 8 % after 2 h at 100 degrees C in degassed n-decane, demonstrating its greatly improved kinetic stability compared to previous [1.1]paracyclophanes. Since 2a undergoes efficient photochemical transformation into the transannular addition product 3a, irradiation of la tends to produce a mixture of products consisting mainly of 3a. Compound 3a, however, reverts thermally to 2a in a process of half life 40 min at 55 degrees C; the activation parameters for this process are deltaH(not equal to)= 21.1 +/- 0.8 kcalmol(-1) and deltaS(not equal to) = -10.5 +/- 2.6 cal K(-1)mol(-1). Thus, on heating 3a in benzene and cooling the resultant solution, 2a is obtained as orange-red crystals. X-ray crystallographic analysis of 2a reveals benzene rings bent to the highest degree ever reported for a paracyclophane, with their face-to-face arrangement in unusually close proximity. The shortest nonbonding interatomic distance is 2.376 A; less than the sum of the van der Waals radii by more than 1.0A. The generation of related substituted [1.1]paracyclophanes and their kinetic stabilities are also reported.     

Novel ligands based on bromosubstituted hydroxycarbonyl [2.2]paracyclophane derivatives: synthesis and application in asymmetric catalysis

New planar-chiral hydroxycarbonyl [2.2]paracyclophane derivatives, 4-acetyl-13-bromo-5-hydroxy[2.2]paracyclophane (Br-АНРС, 63%) and 4-benzoyl-13-bromo-5-hydroxy[2.2]paracyclophane (Br-BHPC, 53%), were synthesized and reacted with the enantiomers of α-phenylethylamine to form corresponding Schiff bases, 12-bromo-4-hydroxy-5[1-(1-phenyl-ethylimino)-ethyl]-[2.2]paracyclophane and 12-bromo-4-hydroxy-5[1-(1-phenyl-ethylimino)-(phenyl)methylen-[2.2]paracyclophane. The diastereomers of the imines were resolved and their absolute configurations and consequently the corresponding configurations of the enantiomers of Br-АНРС were determined by X-ray diffraction. Enantiomerically pure Schiff bases were applied as ligands to form catalysts for the enantioselective addition reaction of diethylzinc with benzaldehyde where 1-phenylpropanol was obtained with 77–91% ee.     

Ab initio studies of benzocyclopropenone, benzocyclopropenone-containing

Ab initio calculations were carried out on cyclopropenone, 1, benzocyclopropenone, 2, the benzocyclopropenone-containing [2.2]paracyclophane derivative tetracyclo[8.3.2.(4,7)O(11,13)]heptadeca-1(13),4,6,10,14,16-hexaen-12-one, 3, its decarbonylation product tricyclo[8.2.2.2(4,7)]hexadeca-1(12), 4,6,10,13-pentaen-15-yne, 5, a benzyne intermediate, and the bridged benzobarrelene derivative, pentacyclo[5.5.2.2.(1,4)O(4,14)O(10,13)]hexadeca-2,7,9,13,15-pentaene, 6. These calculations suggest that benzocyclopropenone-containing [2.2]paracyclophane, 3, and highly strained bridged benzobarrelene, 6, could exist as stable species. Both aryl rings of the benzocyclopropenone derivative 3 are predicted to be distorted from planarity. This distortion relieves some angle strain present in planar benzocyclopropenone due to the presence of the annulated three-membered ring. Calculations on benzobarrelene, 8, and [2.2]paracyclophane, 4, were performed for comparison to gain a better understanding of the strain borne in bridged benzobarrelene 6. The activation barrier for the intramolecular [4 + 2] cycloaddition of 5 to give 6 was estimated at 18.8 kcal/mol while that for the corresponding [2 + 2] cycloaddition, giving the less stable 9, was 54.5 kcal/mol. The [2 + 2] cycloaddition's transition state was twisted in a manner reminiscent of the conservation of orbital symmetry prediction for an unstrained system.     

E,E-1,4-二[2′,2″-(苯并噁唑基乙烯基)]苯及其衍生物的合成和光性能研究

合成了E,E-1,4-二[2′,2″-(苯并(口恶)唑基乙烯基)]苯及衍生物共14种,测定了它们的熔点、红外光谱、核磁共振氢谱、紫外吸收光谱和荧光发射光谱、荧光量子产率及激光性能。     

New chiral β-diketones based on [2.2]paracyclophane

Two chiral β-diketones, 1,3-bis[(S)-(4-[2.2]paracyclophanyl)]propane-1,3-dione (BPPD) and [1-(S)-(4-[2.2]paracyclophanyl)-3-phenyl]propane-1,3-dione (PPPD), were synthesized by acylation of (S)-4-acetyl[2.2]paracyclophane with methyl esters from the corresponding carboxylic acids. 4-Acetyl[2.2]paracyclophane was synthesized in a quantitative yield by the reaction of [2.2]paracyclophane-4-carboxylic acid with methyllithium.     

Zur frage transanularer II-II-wechselwirkungen im [2.2]metacyclophan, [2.2]Paracyclophan und 2,2′-spirobiindan

Concerning the question of transanular II-II-interactions in [2.2]metacyclophane, [2.2]paracyclophane and 2,2′-spirobiindane.From the quotient of the two dissociation constants (K₁/K₂) of [2.2]metacyclophane-bis-chromtricarbonyl (9·0 ± 1·9) it was concluded that there are no transanular II-II-interactions between the two benzene rings. The corresponding values for the bis-chromtricarbonyl-complexes of 2,2′-spirobiindane and [2.2]paracyclophane are 8·0 ± 1·5 and 10⁴, resp. These results are supported by IR-spectroscopical data of the CO-frequencies of the Cr(CO)₃-complexes of [2.2]metacyclophane and some derivatives, of 2,2′-spirobiindane and [2.2]paracyclophane.Moreover, UV-spectroscopic studies of tetracyanoethylene complexes of arenes are shown to be insignificant with regard to transanular II-II-interactions.     

Synthesis of a new polyfluorinated vinylogue of tetrathiafulvalene through 1,3-dipolar cycloaddition of ethyl beta-bromoperfluorodithiocrotonate with dimethyl acetylenedicarboxylate

The ethyl ester of beta-bromoperfluorodithiocrotonic acid reacts with dimethyl acetylenedicarboxylate to give 1,4-difluoro-2,3-bis(trifluoromethyl)-but-2-ene-1,4-diylidene-2,2'-bis(4',5'-dicarbomethoxy-1',3'-dithiole) (4), a new type of vinylogue of tetrathiafulvalene. The thermal transformations of this compound lead, depending on the temperature, to the formation of the cyclization products: 11,14-difluoro-2,3,8,9-tetra(carbomethoxy)-12,13-bis(trifluoromethyl)-1,4,7,10-tetrathiadispiro[4.0.4.4]tetradeca-2,8,11,13-tetraene (8) or 5,8-difluoro-6,7-bis(trifluoromethyl)-2,3-bis(carboxymethyl)-1,4-benzodithiine (11).     

Electronic states of cyclophanes with small bridges

Electronic absorption and magnetic circular dichroism were recorded for five cyclophanes with ethano bridges: [2.2]paracyclophane, (1,2,4)[2.2.2]cyclophane, (1,2,4;1,2,5)[2.2.2]cyclophane, (1,2,3,4,5,6)(1,2,3,4,5,6)cyclophane, and trans-[2.2]metacyclophane. Spectral and structural analyses were based on geometry optimization and calculations of transition energies, carried out using density functional theory methods. The assignments have been proposed for several electronic transitions observed in the region below 52,000 cm(-1). The observation of transitions which should be forbidden in the high D(2h) symmetry [2.2]paracyclophane suggests a twisted ground state structure of D(2) symmetry, although the former structure with large amplitude vibrations at room temperature cannot be excluded. The PBE0 functional turned out to appropriately reproduce the inter-ring distances and electronic transition energies.     

对甲苯磺酸催化下二乙酰苯与含有羟基的苯甲醛的Aldol缩合反应

以对甲苯磺酸(p-TsOH)作催化剂, 二乙酰苯与含有羟基的苯甲醛发生aldol缩合反应, 合成了3个1,3-双[3-(取代苯基)丙烯酰基]苯衍生物1～3, 3个1,4-双[3-(取代苯基)丙烯酰基]苯衍生物4～6和2个中间体7, 8, 中间体7, 8再与含有羟基的苯甲醛发生aldol反应合成了3个1-[3-(4-羟基苯基)丙烯酰基]-4-[3-(取代苯基)丙烯酰基]苯衍生物9～11, 反应均能在2～6 d内完成, 操作和后处理简便. 以上11个新化合物均未见报道, 其结构经1H NMR, IR, MS和HRMS加以确证.     

Structure Determination of an Unusual [2.2]paracyclophane Derivative by NMR Spectroscopy

Our ongoing study on cycloaddition reactions of dienes with different dienophiles afforded a great variety of derivatives with interesting molecular structures and electronic behavior. A new type of angularly annelated [2.2]paracyclophane (3) has been synthesize by the Diels–Alder reaction of 4-(2-propenyl[2.2]paracyclophane (1) and 1,4-benzoquinone (2) under high pressure conditions. The structure determination of this compound has been achieved by NMR measurements and semiempirical calculations.     

Heats of formation of [2.2]paracyclophane-1-ene and [2.2]paracyclophane-1,9-diene - an experimental study

The enthalpies of formation [Delta(g)] of tricyclo[8.2.2.2(4,7)]hexadeca-1(13),2,4(16),5,7(15),10(14),11-heptaene (2, 1,2-dehydro[2.2]paracyclophane or [2.2]paracyclophane-1-ene) and tricyclo[8.2.2.2(4,7)]hexadeca-1(13),2,4(16),5,7(15),8,10(14),11-octaene (3, 1,2,9,10-dehydro[2.2]paracyclophane or [2.2]paracyclophane-1,9-diene) have been determined by measuring their heats of combustion in a microcalorimeter and their heats of sublimation by the transpiration method. Values of the strain energies (SE) [SE(2) = 34.7 kcal mol(-)(1), SE(3) = 42.0 kcal mol(-)(1)] have been derived from the gas-phase heats of formation and are compared with those from MM3 and PM3 calculations and with the corresponding value SE(1) = 30.1 kcal mol(-)(1) for the parent tricyclo[8.2.2.2(4,7)]hexadeca-1(13),4(16),5,7(15),10(14),11-hexaene (1, [2.2]paracyclophane). The higher strain energies of 2 and 3 (by 4.6 and 11.9 kcal mol(-)(1)) are in accord with the well-known increased reactivities of their aromatic rings as a consequence of their increased bending. As revealed by an X-ray crystal structure analysis, the bending in the monoene 2 corresponds to that of 1 and 3 at one of two bridging corners.