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1.
Org Lett ; 2020 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-32011895

RESUMO

We have developed a method for the arylation of nitronyl nitroxide without using its transition metal complex as a nucleophile. Various nitronyl nitroxide-substituted π-electronic compounds can be obtained from the parent nitronyl nitroxide and the corresponding aryl iodides using a combination of zero-valent palladium catalysts and a 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl ligand in the presence of sodium tert-butoxide. The utility of the method has been demonstrated by the direct synthesis of open-shell compounds with giant π-electronic systems, such as 10P.

2.
Chem Asian J ; 15(3): 406-414, 2020 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-31922659

RESUMO

Molecular functions depend on conformations and motions of the corresponding molecular species. An air-water interface is a suitable asymmetric field for the control of molecular conformations and motions under a small applied force. In this work, double-paddled binuclear PtII complexes containing pyrazole rings linked by alkyl spacers were synthesized and their orientations and emission properties dynamically manipulated at the air-water interface. The complexes emerge from water with concurrent variation of interface orientation of the planes of the PtII complexes from perpendicular to parallel during mechanical compression suggesting a unique 'submarine emission'. Phosphorescence of the complexes is quenched at the air-water interface prior to monolayer formation with intensities subsequently rapidly increasing during monolayer compression. These results indicate that asymmetric reactions and motions might be controlled by applying mechanical force at the air-water interface.

3.
Data Brief ; 25: 104300, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31453290

RESUMO

Herein we report the synthesis, characterization data and photophysical properties of iridium(III) complexes having N-alkylated salicylaldimine and 2-phenylpyridine ligands. The structures of novel iridium complexes were assigned by 1H and 13C NMR, 1H-1H COSY, NOESY, HMQC, HMBC, HRMS, IR and XRD analysis. For further information, we obtained photophysical properties in solution and crystalline states.

4.
ACS Omega ; 4(6): 10031-10035, 2019 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-31460095

RESUMO

A liquescent salt based on an N-pentylphenothiazine radical cation (1 •+ ·NTf 2 - ) exhibited a unique crystal-crystal phase transition from a paramagnetic orange solid to a diamagnetic green solid induced by brief, weak, and pinpoint mechanostress. Electron spin resonance and electronic spectroscopies revealed that this unprecedented solid-state spin controllability was attributable to mechanostress-triggered sequential association of the highly mobile radical species occurring under neat conditions.

5.
Inorg Chem ; 58(14): 9076-9084, 2019 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-31247829

RESUMO

In this paper, we describe the first phosphorescent molecules that do not exhibit the concentration quenching in the homogeneous solution state throughout the entire range of concentrations. A series of newly designed polymethylene-vaulted trans-bis[2-(iminomethyl)imidazolato]platinum(II) complexes (1a, n = 10; 1b, n = 12; 1c, n = 14) was prepared by treating [PtCl2(CH3CN)2] with the corresponding N,N'-bis[(1H-imidazol-2-yl)methylene]-1,ω-alkanediamines. The trans coordination and vaulted structures of 1 have been unequivocally established from X-ray diffraction studies. When the concentration of a clear homogeneous solution of 1a-c in organic solvents increases from the diluted to the saturated state, the emission intensity and quantum efficiency increase continuously without concentration quenching at ambient temperature. This is in contrast to the emission profiles of other analogues 2-4 and typical AIEgens, which show ordinary concentration quenching under the same measurement conditions. The present concentration-driven emission enhancement is observed more intensely in a solution of a racemic mixture of 1 in comparison to that of the optically pure solution. Kinetic studies, 1H NMR, XRD analyses, and DFT calculations revealed that this specifically intense emission enhancement of 1 is attributed to an increase in the contribution of a 3MMLCT to 1GS transition, which is caused by the specific ability for the formation of a cofacial association dimer of 1.

6.
Chemistry ; 25(14): 3650-3661, 2019 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-30623493

RESUMO

The heat-resistant properties towards thermal emission quenching of trans-bis[(ß-iminomethyl)aryloxy]platinum(II) complexes bearing 3-iminomethyl-2-naphtholato- (1), 1-iminomethyl-2-naphtholato- (2), 2-iminomethyl-1-naphtholato- (3), and 2-iminomethyl-1-phenolato (4) moieties, and a mechanistic rationale of these properties, are described in this report. Complex 1 a, with N,N'-dipentyl groups, exhibits intense red emission in 2-methyl-2,3,4,5-tetrahydrofuran (2-MeTHF) at 298 K, whereas the analogues 2 a-4 a are less or non-emissive under the same measurement conditions. All four complexes are highly emissive at 77 K. The heat-resistant properties toward thermal emission quenching (Φ298 K /Φ77 K ) increase in the order 1 a (0.52)>2 a (0.09)>3 a (0.02)>>4 a (0.00). We investigated the emission decay and thermal-deactivation processes using density functional theory (DFT), time-dependent (TD) DFT, and double-hybrid density functional theory (DHDF) calculations of N,N'-diethyl forms 1 b-4 b, and discuss the results with a focus on the energy levels, molecular structures, and electronic configurations in the triplet excited states. The energy differences between the triplet metal-ligand charge transfer (3 MLCT) state and minimum-energy crossing point between the lowest triplet state and singlet ground state (MECP) increase in the order 1 a>2 a, 3 a>4 a, consistent with the experimental results for the heat-resistant properties of these complexes. The origin of the present structure dependence of the 3 MLCT-MECP energy gap is ascribed to the ease or difficulty of the high-lying dσ* orbital participating in the MECP upon thermal structural distortion. The structure dependence in energy gaps between the π* and dσ* orbitals, which is key for facilitating the thermal deactivation process, is rationally correlated with the extent of aromaticity on the coordination platforms (1 b>(2 b, 3 b)>4 b).

7.
Chemistry ; 24(48): 12546-12554, 2018 Aug 27.
Artigo em Inglês | MEDLINE | ID: mdl-29863759

RESUMO

The supramolecular chirality of aggregates consisting of achiral trans-bis(salicylaldiminato)NiII complex 1 bearing long alkyl chains can be generated and controlled precisely in a chiral nematic liquid-crystalline (LC) solvent, whereas the complex naturally forms achiral gel fibers in achiral nematic LC solvents and crystals in nonmesogenic solvents. The direction and intensity of the helicity of the gel fibers of 1 in the LC gel state can be adjusted by means of the nature of the helical twisting and the concentration of the chiral dopants. Helicity control was precisely detected in the circular dichroism (CD) spectra of LC gels and by direct SEM observation of the dried gel fibers. XRD analysis revealed that the flexibility of the herringbone-based lamellar alignment of this complex is the key to the LC-specific gelation and helicity control of the gel fibers.

8.
Dalton Trans ; 45(48): 19257-19268, 2016 Dec 06.
Artigo em Inglês | MEDLINE | ID: mdl-27891543

RESUMO

The participation of neighbouring nitrogen lone pairs in the chromogenic control of trans-bis(salicylaldiminato)Pt(ii) platforms was examined, using newly designed Pt analogues bearing salicylaldehyde hydrazone ligands. A series of non-vaulted and vaulted Pt complexes (1-5) with salicylaldehyde hydrazones as trans-coordinated bidentate ligands were synthesized and characterized with regard to the chromogenic behaviour of the trans-bis(salicylaldiminato)Pt(ii) coordination platforms. X-ray diffraction and 2D NMR data demonstrated that, in the case of the non-vaulted N-monomethyl complexes 1, there was significant participation of neighbouring N(2) lone pairs in the d-π conjugation of the trans-bis(salicylaldiminato)Pt(ii) platforms owing to conformational fixation arising from intramolecular hydrogen bonding. In contrast, the lone pairs of the N,N-dimethyl analogues 2 made a much less significant contribution to the extension of the d-π conjugation, due to their high conformational mobility. Complexes 1-5 were found to have structure-dependent chromogenic properties in the solution state, such that the absorption spectra of the N-methyl, short-vaulted complexes 1 and 3 exhibited significant hypsochromic shifts relative to the N,N-dimethyl, long-vaulted analogues 2 and 5, which had spectra very similar to that of the trans-bis(salicylaldiminato)Pt(ii) complex 6. The introduction of MeO groups at the 3- and 5 positions on the aromatic rings of 1 and 2 gave rise to significant hypsochromic and bathochromic shifts, respectively. In addition, νmax - ET(30) plots for various solvents revealed that complexes 1-5 exhibit negative solvatochromism, in which the data obtained in alcoholic solvents are hypsochromically separated from those in non-alcoholic solvents for 1 and 3, an effect that is not observed for 2 and 5. Complexes 1-5 also exhibit emission enhancement upon addition of excess CH3SO3H in dimethyl sulfoxide, and a significant effect of the linker on quantum yields (Φ77 K) was observed in the case of the vaulted complexes. Density functional theory calculations (B3LYP/6-31G*, LanL2DZ) determined that the structure dependence of the chromogenic behaviour of these non-vaulted and polymethylene-vaulted hydrazone complexes can be attributed to variations in the participation of neighbouring nitrogen lone pairs in the d-π conjugation on the trans-bis(salicylaldiminato)Pt(ii) coordination platforms.

9.
Chemistry ; 22(16): 5712-26, 2016 Apr 11.
Artigo em Inglês | MEDLINE | ID: mdl-26934178

RESUMO

The synthesis, structure, and flapping motion of clothespin-shaped binuclear trans-bis(salicylaldiminato)palladium(II) complexes (anti-1) with 4-azaheptamethylene linkers bearing amide (a-g), urethane (h), or urea (i) functionalities are described in this report. Various 2D (1)H NMR experiments and XRD analyses indicate that the amide- and urethane-linked anti-1 a,b,d-h complexes exist as equilibrated mixtures of major and minor conformers I and II in CDCl3, whereas the complexes anti-1 c and i were observed as a single species. The mapping of NOESY cross-peaks between conformers I and II revealed that the equilibration of the major and minor conformers of anti-1 a,b,d-h proceeds by two pathways, namely a nonrotatory flapping motion of the coordinated blades and a nonflapping rotation of C-N bonds, whereas the equilibration of anti-1 c proceeds by simultaneous flapping and rotation motions. Kinetic studies carried out by means of (1)H-(1)H EXSY experiments revealed that 1) the ΔG(≠) 298K values for the flapping motion are controlled remotely by the steric and electronic effects of the RCON functionalities and 2) the activation parameters for the nonrotatory flapping process are identical to those for the nonflapping peptide rotation in the complexes anti-1 a,b,d-h, which indicates that the present multistep conformational transformation induced by the flapping motion is controlled by the rate-determining pyramidalization/depyramidalization (i.e., sp(2)/sp(3) interconversion) of the nitrogen atoms of the functionalities. The static and controllable molecular mobility of anti-1 bearing peptide linkers has been discussed by comparison with the dynamic behavior of its analogues anti-2-4 with flexible polymethylene linkers.

10.
Chemistry ; 21(37): 12927-39, 2015 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-26212577

RESUMO

Heterometal arrays in molecular aggregations were obtained by the spontaneous and ultrasound-induced gelation of organic liquids containing the chiral, clothespin-shaped trans-bis(salicylaldiminato) d8 transition-metal complexes 1. Heterometallic mixtures of complexes 1 a (Pd) and 1 b (Pt) underwent strict heterochiral aggregation entirely due to the organic shell structure of the clothespin shape, with no effect of the metal cores. This phenomenon provides an unprecedented means of generating highly controlled heterometallic arrangements such as alternating sequences [(+)-Pd(-)-Pt(+)-Pd(-)-Pt⋅⋅⋅] as well as a variety of single metal-enriched arrays (e.g., [(+)-Pt(-)-Pd(+)-Pd(-)-Pd(+)-Pd(-)-Pd⋅⋅⋅] and [(+)-Pd(-)-Pt(+)-Pt(-)-Pt(+)-Pt(-)-Pt⋅⋅⋅]) upon the introduction of an optically active masquerading unit with a different metal core in the heterochiral single-metal sequence. The present method can be applied to form various new aggregates with optically active Pd and Pt units, to allow 1) tuning of the gelation ultrasound sensitivity based on the different hearing abilities of the metal units; 2) aggregation-induced chirality transfer between heterometallic species; and 3) aggregation-induced chirality enhancement. A mechanistic rationale is proposed for these molecular aggregations based on the molecular structures of the units and the morphologies of the aggregates.

11.
Chemistry ; 21(25): 9171-8, 2015 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-25962532

RESUMO

Unprecedented intense fluorescent emission was observed for a variety of flavin compounds bearing a perpendicular cyclic imide moiety at the C7 position of an isoalloxazine platform. A series of alloxan-substituted flavins was prepared selectively by reduction of the corresponding N-aryl-2-nitro-5-alkoxyanilines with zinc dust and subsequent reaction with alloxan monohydrate in the presence of boric acid. Analogues bearing oxazolidine-2,4-dione functionality were obtained on methylation of the alloxan-substituted flavins with methyl iodide and subsequent rearrangement in the presence of an inorganic base. The flavin compounds exhibit intense white-green fluorescent emission in the solution state under UV excitation at 298 K, with emission efficiencies Φ298 K greater than 0.55 in CH3 CN, which are higher than the values for all reported flavin compounds under similar conditions. The highest Φ298 K value of 0.70 was obtained in CH3 CN for isoalloxazine bearing C7-alloxan and N10-2,6-diisopropylphenyl groups. The temperature dependence of the emission intensities indicates that the pronounced emission properties at 298 K are attributable to the highly heat resistant properties towards emission decay with increasing temperature. Mechanistic studies, including X-ray diffraction analysis, revealed that the good emission properties and high heat resistance of the alloxan-substituted flavins are due to a synergetic effect of the associative nature of the C7-alloxan unit and the repulsive nature of the perpendicular bulky substituents at the C7 and N10 positions.


Assuntos
Aloxano/química , Compostos de Anilina/química , Flavinas/química , Corantes Fluorescentes/química , Compostos de Anilina/síntese química , Espectrofotometria Ultravioleta , Difração de Raios X
12.
Dalton Trans ; 43(26): 10074-85, 2014 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-24872001

RESUMO

The synthesis, structure, and solid-state emission of vaulted trans-bis(salicylaldiminato)platinum(ii) complexes 1-3 with halogen functionalities are described and compared with the non-substituted analogues. Chloro-substitution provided an improvement of the low emission properties of short-vaulted, non-substituted complexes 1 and 2 in the crystalline state at ambient temperature, while the intense emission of long-vaulted analogues 3 remained unchanged. Bromo-substituted crystals also emit intensively, while the fluoro analogue is non-emissive under the same conditions. Temperature-dependent emission spectra indicate that all chloro- and bromo-substituted crystals with enhanced emission properties at ambient temperature exhibit improved heat resistance properties towards emission decay with the halogen functionalities. X-ray diffraction studies revealed that such a positive effect of halogenation for the enhancement of solid-state emission is due to significant molecular constraints in the crystals by a combination of the vaulted structure and three-dimensional HX hydrogen bonding interactions.

13.
Chemistry ; 20(23): 6991-7000, 2014 Jun 02.
Artigo em Inglês | MEDLINE | ID: mdl-24753131

RESUMO

The synthesis, structure, and solution-state behavior of clothespin-shaped binuclear trans-bis(ß-iminoaryloxy)palladium(II) complexes doubly linked with pentamethylene spacers are described. Achiral syn and racemic anti isomers of complexes 1-3 were prepared by treating Pd(OAc)2 with the corresponding N,N'-bis(ß-hydroxyarylmethylene)-1,5-pentanediamine and then subjecting the mixture to chromatographic separation. Optically pure (100 % ee) complexes, (+)-anti-1, (+)-anti-2, and (+)-anti-3, were obtained from the racemic mixture by employing a preparative HPLC system with a chiral column. The trans coordination and clothespin-shaped structures with syn and anti conformations of these complexes have been unequivocally established by X-ray diffraction studies. (1)H NMR analysis showed that (±)-anti-1, (±)-anti-2, syn-2, and (±)-anti-3 display a flapping motion by consecutive stacking association/dissociation between cofacial coordination planes in [D8]toluene, whereas syn-1 and syn-3 are static under the same conditions. The activation parameters for the flapping motion (ΔH(≠) and ΔS(≠)) were determined from variable-temperature NMR analyses as 50.4 kJ mol(-1) and 60.1 J mol(-1) K(-1) for (±)-anti-1, 31.0 kJ mol(-1) and -22.7 J mol(-1) K(-1) for (±)-anti-2, 29.6 kJ mol(-1) and -57.7 J mol(-1) K(-1) for syn-2, and 35.0 kJ mol(-1) and 0.5 J mol(-1) K(-1) for (±)-anti-3, respectively. The molecular structure and kinetic parameters demonstrate that all of the anti complexes flap with a twisting motion in [D8]toluene, although (±)-anti-1 bearing dilated Z-shaped blades moves more dynamically than I-shaped (±)-anti-2 or the smaller (±)-anti-3. Highly symmetrical syn-2 displays a much more static flapping motion, that is, in a see-saw-like manner. In CDCl3, (±)-anti-1 exhibits an extraordinary upfield shift of the (1)H NMR signals with increasing concentration, whereas solutions of (+)-anti-1 and the other syn/anti analogues 2 and 3 exhibit negligible or slight changes in the chemical shifts under the same conditions, which indicates that anti-1 undergoes a specific heterochiral association in the solution state. Equilibrium constants for the dimerizations of (±)- and (+)-anti-1 in CDCl3 at 293 K were estimated by curve-fitting analysis of the (1)H NMR chemical shift dependences on concentration as 26 M(-1) [KD(racemic)] and 3.2 M(-1) [KD(homo)], respectively. The heterochiral association constant [KD(hetero)] was estimated as 98 M(-1), based on the relationship KD(racemic) = 1/2 KD(homo) +1/4 KD(hetero). An inward stacking motif of interpenetrative dimer association is postulated as the mechanistic rationale for this rare case of heterochiral association.

14.
Dalton Trans ; 42(45): 15953-66, 2013 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-23963158

RESUMO

Pd- and Pt-bound bis-metalated peptides were synthesised by the condensation of Pd- or Pt-aldimine-complex-bound glutamic acids to afford the four possible metal isomers of bis-Pd and bis-Pt-homometalated dipeptides and PdPt- and PtPd-heterometalated dipeptides without metal disproportionation. Ultrasound-induced self-assembly of these bis-metalated peptides proceeded effectively to afford supramolecular gels that displayed well-ordered metal arrays. The formation of parallel ß-sheet type aggregates through interpeptide amide-amide hydrogen bonding was confirmed by IR, scanning electron microscopy (SEM), and synchrotron X-ray diffraction analyses (WAXS and SAXS). The mechanism of the ultrasound-induced self-assembly of the metalated dipeptides was elucidated via kinetic and association experiments by (1)H NMR, in which ultrasound-triggered dissociation of intramolecular hydrogen bonds between the chloride ligands of the Pd- and Pt-complexes and amides initially occurred. This was followed by the formation of intermolecular amide-amide hydrogen bonds, which afforded the corresponding oligomeric peptide self-assembly as the nucleus for supramolecular aggregation. The observed first-order relationship of the gelation rate versus the sonication frequency suggested that the microcavitation generated under sonication conditions acted as a crucial trigger and provided a reaction field for efficient self-assembly.


Assuntos
Dipeptídeos/química , Géis/química , Ácido Glutâmico/química , Paládio/química , Platina/química , Sonicação , Complexos de Coordenação/química , Ligação de Hidrogênio , Iminas/química , Modelos Moleculares , Espalhamento a Baixo Ângulo , Difração de Raios X
15.
Chemistry ; 19(29): 9497-505, 2013 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-23780879

RESUMO

Morphology control for intense solid-state phosphorescence of non-emissive, but potentially emissive crystals of platinum complexes and the mechanistic rationale are described. A series of trans-bis(salicylaldiminato)platinum(II) complexes bearing linear alkyl chains (1a: n=5; 1b: n=8; 1c: n=12; 1d: n=14; 1e: n=16; 1f: n=18) was synthesized and the solid-state emission properties were examined by using crystals/aggregates prepared under various precipitation conditions. Crystals of 1e, prepared using "kinetic" conditions including rapid cooling, high concentrations, and poor solvents, emit intensive yellow phosphorescence (λ(max)=545 nm) under UV irradiation at 298 K with an absolute quantum efficiency of 0.36, whereas all the crystals of 1a-1f prepared using "thermodynamic" conditions including slow cooling, low concentrations, and good solvents were either non- or less emissive with Φ(298K) values of 0.12 (1a), 0.11 (1b), 0.10 (1c), 0.07 (1d), 0.02 (1e), and 0.02 (1f) under the same measurement conditions. The amorphous solid 1e, prepared by rapid cooling and freeze-drying, was also non-emissive (Φ(298K)=0.02, 0.02). Temperature-dependent emission spectra showed that the kinetic crystals of 1e exhibit high heat-resistance towards emission decay with increasing temperature, whereas the amorphous solid 1e is entirely heat-quenchable. This is a rare example of the change from a non-emissive crystal into a highly emissive crystal by morphology control through crystal engineering. Emission spectra and powder X-ray diffraction (XRD) patterns of the emissive, kinetic crystals of 1e are clearly distinct from those of the less emissive, thermodynamic crystals of 1a-1f. Single-crystal XRD unequivocally establishes that the thermodynamic crystals of 1d have a multilayered lamellar structure supported by highly regulated, consecutive π-stacking interactions between imine moieties, whereas the kinetic crystals of 1e have a face-to-edge lamellar structure with less stacking. These results lead to the conclusion that 1) morphology control of long-chained complexes exclusively generates a metastable herringbone-based lamellar packing motif that exhibits intense emission and high heat-resistance, while 2) a thermodynamically stable, highly regulated, consecutive stacking motif is unfavorable for solid-state emission.

16.
Acta Crystallogr C ; 69(Pt 5): 503-5, 2013 May.
Artigo em Inglês | MEDLINE | ID: mdl-23629901

RESUMO

rac-Bis{µ-trans-2,2'-[pentane-1,5-diylbis(azanediyl)]ditroponato}dipalladium(II), [Pd2(C19H20N2O2)2], has been synthesized and fully characterized using single-crystal X-ray diffraction, (1)H NMR, FT-IR and mass spectroscopy. The trans coordination, vaulted structure and anti conformation have been unequivocally established from the X-ray diffraction studies. This is the first example of a bis(aminotroponato)palladium complex. In the crystalline state, the molecule has twofold symmetry and each molecular unit undergoes intermolecular offset π-stacking of the tropone rings to afford heterochiral interpenetrating dimers that are aligned in a lamellar manner with a herringbone packing motif.

17.
Chemistry ; 19(15): 4798-811, 2013 Apr 08.
Artigo em Inglês | MEDLINE | ID: mdl-23418050

RESUMO

The synthesis, structure, and solid-state emission of vaulted trans-bis(salicylaldiminato)platinum(II) complexes are described. A series of polymethylene (1: n=8; 2: n=9; 3: n=10; 4: n=11; 5: n=12; 6: n=13) and polyoxyethylene (7: m=2; 8: m=3; 9: m=4) vaulted complexes (R=H (a), 3-MeO (b), 4-MeO (c), 5-MeO (d), 6-MeO (e), 4-CF3O (f), 5-CF3O (g)) was prepared by treating [PtCl2(CH3CN)2] with the corresponding N,N'-bis(salicylidene)-1,ω-alkanediamines. The trans coordination, vaulted structures, and the crystal packing of 1-9 have been unequivocally established from X-ray diffraction studies. Unpredictable, structure-dependent phosphorescent emission has been observed for crystals of the complexes under UV excitation at ambient temperature, whereas these complexes are entirely nonemissive in the solution state under the same conditions. The long-linked complex crystals 4-6, 8, and 9 exhibit intense emission (Φ77K =0.22-0.88) at 77 K, whereas short-linked complexes 1-3 and 7 are non- or slightly emissive at the same temperature (Φ77K <0.01-0.18). At 298 K, some of the long-linked crystals, 4a, 4b, 5c, 5e, 6c, 6e, and 9b, completely lose their high-emission properties with elevation of the temperature (Φ298K <0.01-0.02), whereas the other long-linked crystals, 5a, 6a, 9a, and 9d, exhibit high heat resistance towards emission decay with increasing temperature (Φ298K =0.21-0.38). Chromogenic control of solid-state emission over the range of 98 nm can be performed simply by introducing MeO groups at different positions on the aromatic rings. Orange, yellow-green, red, and yellow emissions are observed in the glass and crystalline state upon 3-, 4-, 5-, and 6-MeO substitution, respectively, whereas those with CF3 O substituents have orange emission, irrespective of the substitution position. DFT calculations (B3LYP/6-31G*, LanL2DZ) showed that such chromatic variation is ascribed to the position-specific influence of the substituents on the highest-occupied molecular orbital (HOMO) and lowest-unoccupied molecular orbital (LUMO) levels of the trans-bis(salicylaldiminato)platinum(II) platform. The solid-state emission and its heat resistance have been discussed on the basis of X-ray diffraction studies. The planarity of the trans-coordination sites is strongly correlated to the solid-state emission intensities of crystals 1-9 at lower temperatures. The specific heat-resistance properties shown exclusively by the 5a, 6a, 9a, and 9d crystals are due to their strong three-dimensional hydrogen-bonding interactions and/or Pt···Pt contacts, whereas heat-quenchable crystals 4a, 4b, 5c, 5e, 6c, 6e, and 9b are poorly bound with limited interactions, such as non-, one-, or two-dimensional hydrogen-bonding networks. These results lead to the conclusion that Pt···Pt contacts are an important factor in the heat resistance of solid-state phosphorescence at ambient temperature, although the role of Pt···Pt contacts can be substituted by only higher-ordered hydrogen-bonding fixation.

18.
Chem Commun (Camb) ; 48(33): 3936-8, 2012 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-22297814

RESUMO

A new type of Pt-complex-bound amino acid was synthesized by condensation of a cyclometalated Pt complex with the side-chain residue of N- and C-alkylated glutamic acid. Self-assembly of the Pt-bound lipophilic amino acid afforded a supramolecular gel in organic solvents, which comprised fibrous lamellar aggregates that supported a highly oriented Pt array.


Assuntos
Ácido Glutâmico/química , Compostos Organoplatínicos/química , Platina/química , Modelos Moleculares , Estrutura Secundária de Proteína
19.
J Am Chem Soc ; 133(40): 16054-61, 2011 Oct 12.
Artigo em Inglês | MEDLINE | ID: mdl-21894951

RESUMO

Instant and precise control of phosphorescent emission can be performed by ultrasound-induced gelation of organic liquids with chiral, clothespin-shaped trans-bis(salicylaldiminato)Pt(II) complexes, anti-1. Nonemissive solutions of racemic, short-linked anti-1a (n = 5) and optically pure, long-linked anti-1c (n = 7) in organic liquids are transformed immediately into stable phosphorescent gels upon brief irradiation of low-power ultrasound. Emission from the gels can be controlled by sonication time, linker length, and optical activity of the complexes. Several experimental results indicated that structure-dependent homo- and heterochiral aggregations and ultrasound-control of the aggregate morphology are key factors for emission enhancement.


Assuntos
Géis/química , Substâncias Luminescentes/química , Compostos Organoplatínicos/química , Ultrassom
20.
Chemistry ; 17(21): 5908-20, 2011 May 16.
Artigo em Inglês | MEDLINE | ID: mdl-21495097

RESUMO

A versatile reducing agent, diimide, can be generated efficiently by the aerobic oxidation of hydrazine with neutral and cationic synthetic flavin catalysts 1 and 2. This technique provides a convenient and safe method for the aerobic reduction of olefins, which proceeds with 1 equiv of hydrazine under an atmosphere of O(2) or air. The synthetic advantage over the conventional gas-based method has been illustrated through high hydrazine efficiency, easy and safe handling, and characteristic chemoselectivity. Vitamin B(2) derivative 6 acts as a highly practical, robust catalyst for this purpose because of its high availability and recyclability. Association complexes of 1b with dendritic 2,5-bis(acylamino)pyridine 15 exhibit unprecedented catalytic activities, with the reduction of aromatic and hydroxy olefins proceeding significantly faster when a higher-generation dendrimer is used as a host pair for the association catalysts. Contrasting retardation is observed upon similar treatment of non-aromatic or non-hydroxy olefins with the dendrimer catalysts. Control experiments and kinetic studies revealed that these catalytic reactions include two independent, anaerobic and aerobic, processes for the generation of diimide from hydrazine. Positive and negative dendrimer effects on the catalytic reactions have been ascribed to the specific inclusion of hydrazine and olefinic substrates into the enzyme-like reaction cavities of the association complex catalysts.


Assuntos
Alcenos/química , Flavinas/química , Hidrazinas/química , Imidas/química , Piridinas/química , Catálise , Cátions/química , Dendrímeros/química , Hidrogenação , Estrutura Molecular , Oxirredução
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