Pyrromethene–BF2 complexes as laser dyes:1.

Condensations between 3-X-2,4-dimethylpyrroles (X = H, CH₃, C₂H₅, and CO₂C₂H₅) and acyl chlorides gave derivatives of 3,5,3′,5′-tetramethylpyrromethene (isolated as their hydrochloride salts): 6-methyl, 6-ethyl, 4,4′,6-trimethyl, 4,4′-diethyl-6-methyl, and 4,4′-dicarboethoxy-6-ethyl derivatives for conversion on treatment with boron trifluoride to 1,3,5,7-tetramethylpyrromethene–BF₂ complex (TMP–BF₂) and its 8-methyl (PMP–BF₂), 8-ethyl, 2,6,8-trimethyl (HMP–BF₂),2,6,-diethyl-8-methyl (PMDEP–BF₂), and 2,6-dicarboethoxy-8-ethyl derivatives. Chlorosulfonation converted, 1,3,5,7,8-pentamethylpyrromethene–BF₂ complex to its 2,6-disulfonic acid isolated as the lithium, sodium (PMPDS–BF₂), potassium, rubidium, cesium, ammonium, and tetramethylammonium disulfonate salts and the methyl disulfonate ester. Sodium 1,3,5,7-tetramethyl-8-ethylpyrromethene-2,6-disulfonate–BF₂ complex was obtained from the 8-ethyl derivative of TMP–BF₂. Nitration and bromination converted PMP–BF₂ to its 2,6-dinitro-(PMDNP–BF₂) and 2,6-dibromo- derivatives. The time required for loss of fluorescence by irradiation from a sunlamp showed the following order for P–BF₂ compounds (10⁻³ to 10⁻⁴ M) in ethanol: PMPDS–BF₂, 7 weeks; PMP–BF₂, 5 days; PMDNP–BF₂, 72 h; HMP–BF₂, 70 h; and PMDEP–BF₂, 65 h. Under similar irradiation PMPDS–BF₂ in water lost fluorescence after 55 h. The dibromo derivative was inactive, but each of the other pyrromethene–BF₂ complexes under flashlamp excitation showed broadband laser activity in the region λ 530–580 nm. In methanol PMPDS–BF₂ was six times more resistant to degradation by flashlamp pulses than was observed for Rhodamine-6G (R-6G). An improvement (up to 66%) in the laser power efficiency of PMPDS–BF₂ (10⁻⁴ M in methanol) in the presence of caffeine (a filter for light <300 nm) was dependent on flashlamp pulse width (2.0 to 7.0 μsec).     

Biimidazol-2-yl–BF2 complexes

Nonfluorescent 4,4′,5,5′-tetramethyl- and 4,5,4′,5′-bistetramethylene biimidazol-2-yls 5 and 6 combined with boron trifluoride to give the tetramethyl and bistetramethylenebiimidazol-2-yl–BF₂ complexes 9 and 10 isolated as strongly fluorescent BF₃ salts, λ_f (dichloromethane): 377 nm Φ 0.93 and 386 nm Φ 0.90. Similarly, fluorescent bibenzimidazol-2-yl 7 , λ_f (ethanol), 370 nm Φ 0.14, gave a BF₂ complex 11 isolated as a BF₃ salt λ_f (ethanol), 417 nm Φ 0.68.     

Laser active cyanopyrromethene–BF2 complexes

Treatment with a mixture of formic and hydrobromic acids converted ethyl 3,4-diethyl-5-methyl-pyrrole-2-carboxylate 7a to 3,3′,4,4′-tetraethyl-5,5′-dimethylpyrromethene hydrobromide 8a presumably via the condensation of α-unsubstituted and α-formylpyrrole intermediates 7c and 7e formed in situ. The corresponding 6-cyanohexaalkylpyrromethane 9a was obtained by the addition of hydrogen cyanide to the pyrromethene 8a and was oxidized with bromine to an unstable pyrromethene 10a , an intermediate converted to 1,2,6,7-tetraethyl-3,5-dimethyl-8-cyanopyrromethene–BF₂ complex 3 , (PM TEDC), λ_las (plastic) 613–639 nm, in a reaction with boron trifluoride etherate. Ethyl 3,4,5-trimethylpyrrole-2-carboxylate 7b was similarly converted to 1,2,3,5,6,7-hexamethyl-8-cyanopyrromethene–BF₂ complex 4 , (PM HMC), λ_las (plastic) 615–639 nm. Immediately after formation by a condensation between propionyl chloride and 2,4-dimethyl-3-cyanopyrrole 16 , unstable 3,3′,5,5′-tetramethyl-6-ethyl-4,4′-dicyanopyrromethene hydrochloride 17 was treated with boron trifluoride etherate to give 1,3,5,7-tetramethyl -2,6-dicyano-8-ethylpyrromethene–BF₂ complex 18 , λ_las (ethanol) 540–565 nm.     

Fluorescent tricyclic β-azavinamidine–BF2 complexes

Boron trifluoride reacted with dipyrid-2-ylamine 6 , its N-methyl and 6,6′-dimethyl derivatives 8 and 10 , and 3,3′,5,5′-tetraphenyl-6-azapyrromethene 13 to give fluorescent β-azavinamidine (1,3,5-triazapenta-1,3-diene) dyes: 10-azapyridomethene–BF₂ complex 5 (λ_f 422 nm, λ_las 426 nm), its quaternary 10-methyl tetrafluoroborate and 4,6-dimethyl derivatives 9 (λ_f 362 nm) and 11 (λ_f 416 nm), and 1,3,5,7-tetraphenyl-8-azapyrromethene–BF₂ complex 17 (λ_f 696 nm). Treating 3,3′,4,4′-tetraphenyl-5,5′,6-trimethylpyrromethene (prepared in situ from ethyl 3,4-diphenyl-5-methylpyrrole-2-carboxylate in a reaction with acetyl chloride) with boron trifluoride gave 1,2,6,7-tetraphenyl-3,5,8-trimethylpyrromethene–BF₂ complex 21 . Absorption for the vinamidine chromophore differed from that for the β-azavinamidine chromophore by a hypsochromic shift of 86 nm in a comparison of pyridomethene–BF₂ complex 3 with its 10-aza derivative 5 and by a bathochromic shift of 105 nm in a comparison of the pyrromethene–BF₂ complex 20 with the 8-azapyrromethene–BF₂ complex 17 .     

BF(2) complexes of alpha-alkyl-substituted dipyrrolyldiketones as acyclic anion receptors

alpha-Alkyl-substituted dipyrrolyldiketones have exhibited anion binding behaviours with pyrrole rotations, whose rates depend on the alkyl chain lengths.     

DPP dyes as ligands in transition-metal complexes

The DPP dyes (=diketopyrrolopyrrole) 1 are deprotonated to give the corresponding dianions 2. These are treated with two moles of the transition-metal complexes [L(n)MX]=[(Ph(3)P)(2)MX] (M=Cu, Ag; X=Cl, NO(3)), [(Ph(3)P)AuCl], [(Et(3)P)AuCl], [(tBuNC)AuCl], [(Ph(3)P)(2)PdCl(2)], and [(Ph(3)P)(2)PtCl(2)] to give the novel bismetalated DPP dyes [L(n)MN[C(3)R(1)(O)](2)NML(n)] (4-10). In comparison with the starting materials, these compounds show better solubilities, high fluorescence quantum yields (Phi > or = 80 %), and bathochromic absorptions. The compounds 4 c, 5 a, 6 b, 6 c, 6 e, 7 c, and 8 c were characterized by X-ray crystallography. The copper and silver atoms in 4 c and 5 a are trigonal planar and are surrounded by the P atoms of the phosphane ligands and the N atom of the DPP dianion 2. Both metals are somewhat forced out-of-plane, and the P(2)M plane and the phenyl planes of R1 are twisted by > or = 70 degrees and < or = 25 degrees, respectively, towards the chromophore plane. The gold atoms in 6-8 are linearly coordinated to one N and one P (6 b, c, e, 7 c) or one C atom (8 c), respectively. The gold atoms are only slightly pressed out-of-plane, and the P substituents are staggered so that there is enough space for the planarization of R(1) into the plane of the chromophore. Compound 8 c shows intermolecular d(10)-d(10) interactions between Au(I) centers of different molecules, and these interactions lead to infinite chains of parallel orientated molecules in a gauche conformation of neighbors (torsion angle=150 degrees) in the crystal.     

Selective iodinated dipyrrolyldiketone BF2 complexes as potential building units for oligomeric systems

Selective iodination at the alpha-pyrrole positions of dipyrrolyldiketone BF(2) complexes is a key procedure to afford mono- and bisiodinated derivatives as the starting materials of the coupling reactions for various utility molecules and covalently linked oligomer systems. Iodination can also be applied to the phenylene-bridging receptor dimer to obtain the derivatives selectively iodinated at the terminal alpha-pyrrole position(s).     

BF2 complexes of beta-tetraethyl-substituted dipyrrolyldiketones as anion receptors: potential building subunits for oligomeric systems

Synthesis and anion binding properties of BF2 complexes of beta-tetraethyl-substituted dipyrrolyldiketones, with and without electron-withdrawing ethoxycarbonyl moieties at pyrrole alpha-positions, are reported. The substituents at pyrrole rings of these acyclic anion receptors are found to play a key role to control not only the polarization of binding sites (NH and CH) but also the relative stabilities of the preorganized conformations and the degrees of sterical repulsion, both of which notably affect the affinities for anions.     

Synthesis of acridinedione derivatives as laser dyes

Synthesis of 9-alkyl, 10-alkyl, 9,10-dialkyl, and 10-aryl-3,4,6,7,9,10-hexahydro-1,8(2H,5H)acridinedione (2a–r) are described as a new class of laser dyes. Reactions of diamines with methylene bis(cyclohexane-1,3-dione) yielded the respective bisacridinediones (3a–e). These dyes lase around 478–494 nm and are compared with the standard dye coumarin-102. © 1996 John Wiley & Sons, Inc.     

Organometallic dyes: Part 1. Synthesis of orange to cyan dyes based on donor–conjugated–acceptor chromogenes using ferrocene as the donor group

A novel series of organometallic donor–conjugated–acceptor dyes derived from ferrocene as the donor group have been synthesized via the Knoevenagel reaction of ferrocene carboxaldehyde and various active methylene compounds to give a range of dyes ranging from orange to blue–green in color. The most bathochromic dye is that derived from dialkyl thiobarbituric acid and the least is that derived from the tetralone. The dyes showed an unusual negative solvatochromism as the solvent polarity increased. All dyes synthesized are expected to have some non‐linear optical properties, as evidenced from the pronounced solvatochromism. Copyright © 2001 John Wiley & Sons, Ltd.     

Synthesis of BF2 complexes of prodigiosin type oligopyrroles

We developed a simple, facile route for the synthesis of BF(2) complexes of prodigiosin type oligopyrroles and their cholesterol conjugates. This route gives an access to synthesize any desired meso-aryl-substituted 3-pyrrolyl BODIPYs which were not easily accessible earlier.     

Non–symmetrically p–nitrobenzyl–substituted N–heterocyclic carbene–silver(I) complexes as metallopharmaceutical agents

In the present work, a series of eight new imidazole, 4,5–dichloroimidazole, 4,5–diphenylimidazole and benzimidazole based nitro–functionalized mono–N –heterocyclic carbene (NHC)–silver(I) acetate ( 7a–d ) and bis–NHC–silver(I) hexafluorophosphate complexes ( 8a–d ) were synthesised by the reaction of the corresponding azolium hexafluorophosphate salts ( 6a–d ) with silver(I) acetate and silver(I) oxide in methanol and acetonitrile, respectively. All the synthesised compounds were fully characterized by various spectroscopic techniques and elemental analyses. Additionally, the structure of bis–(1–benzyl–3–(p –nitrobenzyl)–4,5–dichloroimidazole–2–ylidene)silver(I) hexafluorophosphate complex ( 8b ) was confirmed by single crystal X–ray diffraction analysis. Preliminary in vitro antibacterial evaluation was conducted for all the compounds ( 6a–d) , ( 7a–d) , and ( 8a–d) by Kirby–Bauer's disc diffusion method followed by the determination of Minimum Inhibitory Concentration (MIC) from broth macrodilution method against five standard bacteria; two Gram–positive bacterial strains (Staphylococcus aureus and Bacillus subtilis) and three Gram–negative bacterial strains ( Escherichia coli , Shigella sonnei, and Salmonella typhi). All the hexafluorophosphate salts ( 6a – d) were found inactive against the tested bacterial strains and their corresponding mono– and bis–NHC–silver(I) complexes ( 7a–d and 8a–d ) exhibited moderate to high antibacterial activity with MIC value in the range 8–128 μg/mL. In addition, preliminary in vitro anticancer potential of all the silver(I) complexes ( 7a–d and 8a–d ) was determined against the human derived breast adenocarcinoma cells (MCF 7) by MTT assay. All the mono– and bis–NHC–silver(I) complexes ( 7a–d and 8a–d ) orchestrated high anticancer potential with IC₅₀ values ranging from 10.39 to 59.56 nM. In comparison, mono– NHC–silver(I) complexes performed better than the bis–NHC–silver(I) complexes.     

Octaethylporphyrin and expanded porphyrin complexes containing coordinated BF2 groups

In contrast to octaethylporphyrin, which forms a very labile bis-BF(2) complex, treatment of the hexa- and octapyrrolic expanded porphyrins amethyrin and [32]octaphyrin with BF(3).Et(2) under standard reaction and work-up conditions gives rise to stable, non-labile mono- and bis-BF(2) complexes; these were readily characterised by, inter alia, X-ray diffraction analyses.     

Novel Ru-dioxolene complexes as potential electrochromic materials and NIR dyes

A series of Ru(bpy)(2)-dioxolene complexes 1-4 (bpy = 2,2'- bipyridine) and corresponding Ru(dcb)(2)-dioxolene complexes 5-8 (dcbH(2) = 2,2'-bipyridine-4,4'-dicarboxylic acid) have been prepared, and their spectroelectrochemical behavior in solution has been investigated. The complexes show reversible electrochemical behavior accompanied by a strong NIR absorption in their semiquinone forms due to a Ru(dpi) --> sq(pi) MLCT band. Complete quenching of the NIR absorption occurs both upon oxidation (to the quinone form) and upon reduction (to the catechol form) very close to 0 V. The color of the systems can be tuned by using a wide range of ligands. The complexes 5-8 can be anchored onto nanocrystalline inorganic semiconductors allowing incorporation into potential electrochromic devices. As a proof of principle, compound 8 has been adsorbed on nanocrystalline Sb-doped SnO(2) supported on FTO glass, and it displays reversibly switchable electrochromic behavior in the NIR.     

New polar silane–PEO polyester complexes as polymer electrolytes

Trifunctional carbosilanes containing hydroxy and cyano groups have been synthesized in good yields and incorporated into polyether-based electrolytes. The new linear and cross-linked modified PEOs have been characterized by DSC and conductivity measurements. The effect of silane content, the length of the PEO block, glycerol concentration, and temperature on glass transition temperature and conductivity of lithium salts complexes of these materials has been evaluated. The new materials showed improved conductivity (∼ 10⁻⁵ S cm⁻¹) at ambient temperatures compared with unmodified polyethers. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1093–1106, 1998     

Cellulose–hydrazine complexes

Cellulose–hydrazine complexes have been prepared by soaking cellulose fibers in anhydrous hydrazine, and their structures have been investigated by x-ray diffraction. The unit cells for the complexes formed by native ramie (cellulose I) and by Mercerized ramie and Fortisan (both cellulose II) have different dimensions, but all contain sections of four chains; and the x-ray patterns suggest significant changes in the chain stagger, as compared with the uncomplexed structures. The differences between the Mercerized ramie and Fortisan complexes may reflect the differences in morphology and crystallinity of these materials. Reconversion to cellulose is effected by soaking in water. For the cellulose II complexes a hydrate intermediate is observed in this process. The hydrate is a two-chain unit cell and contains approximately one water molecule per glucose residue.     

Lanthanide–imidazole complexes as latent curing agents for epoxy resins

Imidazoles have for some time been recognized as curing agents for epoxy resins. Once the resin and the imidazole compound are mixed there is a relatively short time in which the mixture can be used, since the polymerization (curing) reaction occurs to some extent even at room temperature causing the reaction mixture to thicken. In order to circumvent this problem we have found that imidazoles can be complexed with organo-lanthanide compounds thereby tying up the imidazole and retarding its rate of reaction in the cure of epoxy materials at ambient temperatures. When it is desired to enhance the rate of cure the temperature of the mixture is simply raised. This paper concerns studies of the epoxy cure reaction with the M(THD)₃–IM series. M represents the lanthanide metals Eu, Ho, Pr, Dy, Yb, and Gd, and THD is 2,2,6,6-tetramethyl-3,5-heptanedione. Cure reactions were followed by differential scanning calorimetry and in some cases by infrared spectroscopy. We have demonstrated that these organo-lanthanide–imidazole complexes are effective thermally latent curing agents for epoxy resins. At a temperature of 150°C cure is quite rapid. In the course of these studies it has also been determined that there is an inverse correlation between the lanthanide ionic radius in the complex and the temperature at which the cure reaction occurs. Thus the Yb compound, where the imidazole is most strongly bound, cures at the highest temperature and Pr, where imidazole is bound most weakly, at the lowest. Consistent with these facts is the observation that the Yb compound also gives the longest latency period when mixed with epoxy resin.     

Conformations of 2-phenylethanol and its singly hydrated complexes: UV–UV and IR–UV ion-dip spectroscopy

The structures of 2-phenylethanol and its 1:1 water complexes have been investigated by UV–UV holeburning and IR–UV ion-dip spectroscopy, coupled with ab initio computation. The most populated molecular conformer is stabilized by an intramolecular π-type H-bond and its rotational band contours suggest the incidence of vibronic coupling involving motion of the side chain. Its 1:1 water complexes are associated with two distinct structures – water binds either as a proton donor or an acceptor. In the latter, the intramolecular H-bond is disrupted and the water molecule inserts between the OH and the aromatic ring. A second, extended anti conformer can also be detected.