Modulating structure and properties in organic chromophores: influence of azulene as a building block

Murai, Masahito; Ku, Sung Yu; Treat, Neil D.; Robb, Maxwell J.; Chabinyc, Michael L.; Hawker, Craig J.

doi:10.1039/c4sc01623h

Cited by 79 publications

(50 citation statements)

References 71 publications

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“…1‐Phenylazulene (1 d) : Blue solid; 1 H NMR (400 MHz, CDCl 3 ): δ= 7.15 (t, J =9.6 Hz, 1 H), 7.16 (t, J =9.6 Hz, 1 H), 7.36 (t, J =8.0 Hz, 1 H), 7.41 (d, J =3.6 Hz, 1 H), 7.50 (t, J =7.8 Hz, 2 H), 7.60 (t, J =9.6 Hz, 1 H), 7.62 (d, J =7.6 Hz, 2 H), 8.04 (d, J =3.6 Hz, 1 H), 8.37 (d, J =9.6 Hz, 1 H), 8.58 ppm (d, J =9.6 Hz, 1 H); 13 C NMR (100 MHz, CDCl 3 ): δ= 117.4, 123.0, 123.3, 126.2, 128.6, 129.7, 131.3, 135.2, 135.6, 137.1, 137.3, 137.5, 138.2, 141.7 ppm; HRMS (FAB + ): m / z : calcd for C 16 H 12 : 204.0939 [ M ] + ; found: 204.0933. The analytical data match those reported in the literature …”

Section: Methodssupporting

confidence: 86%

Palladium‐Catalyzed Direct Arylation of Azulene Based on Regioselective C−H Bond Activation

et al. 2016

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An efficient synthesis of arylazulenes involving minimal steps was developed. The combination of Pd(OAc) 2 / XPhos as ac atalysta nd pivalica cid as an additive was key for the direct arylation of CÀHb onds, and the reactionp roceeded preferentially at the 1-and 3-positions of azulene, without heteroatom-containing directing groups. Compared with the traditional cross-coupling protocol, the arylation method described here requires fewer steps and uses commerciallya vailables ynthetic blocks. The degree of conjugation and the optical properties of the resulting azulenec onjugates can be adjusted by simple protonation, whicha llows the current method to be an efficient strategy for exploiting novel azulene-based functional materials.[a] Dr.

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Section: Methodssupporting

confidence: 86%

Palladium‐Catalyzed Direct Arylation of Azulene Based on Regioselective C−H Bond Activation

et al. 2016

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“…[3][4][5] Similarly, the physical, electronic, and optical properties of some natural pigments could offer access to key building blocks for developing bio-derived chromophoric materials. [9][10][11][12][13][14][15][16] Chemically, guaiazulene is a nonalternant hydrocarbon that is notable for its low transition energy to the S 1 state and unusually large S 1 -S 2 gap, [17][18][19][20][21][22][23][24][25][26][27] where S 1 and S 2 refer to the first and second electronically excited states, respectively. 3,8 Among known natural pigments, 6-8 guaiazulene has received recent popularity for its interesting physical and electronic properties.…”

Section: Introductionmentioning

confidence: 99%

“…6-8 Additionally, the non-toxic nature and the accompanying eco-friendly feature of natural dyes could set the stage for chemists to develop "green" routes towards photonic and conductive materials. [17][18][19][20][21][22][23][24][25][26][27] It was shown that extending the conjugation through the seven-membered ring of the parent azulene with aromatic substituents dramatically impacts the optical, electrochemical, and electrochromic properties of the azulenylium carbocation. [9][10][11][12][13][14][15][16][17] As a nontoxic natural product found in the oils of Guajacum officinale and Matricaria chamomilla, as well as in the vibrant-blue mushroom Lactarius indigo, guaiazulene has been approved by the FDA as a cosmetic color additive.…”

Section: Introductionmentioning

confidence: 99%

Chromophoric materials derived from a natural azulene: syntheses, halochromism and one-photon and two-photon microlithography

et al. 2015

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In addition to their use as colorants in diet and cosmetics, various natural dyes possess photophysical properties that could enable their use as modular building blocks for preparing ecofriendly and non-toxic chromophores. Among natural pigments, guaiazulene holds great potential due to its unique optical and electronic properties. Thus, in order to explore and understand the properties of guaiazulene-containing chromophores, a series of 4-styrylguaiazulenes 3a-l were prepared by condensation of the C-4 methyl group of naturally-occurring guaiazulene 1 with various aromatic carboxaldehydes 2a-l. Treating these analogs 3a-l with a strong acid protonates the electron-rich C-3 and reveals a reversible halochromic behavior where the optical energy gap responds predictably to electrondonor strength and degree of π-conjugation. Additionally, acid-doping is accompanied by efficient fluorescence switch-on, where 3e(H+) and 3g(H+) exhibited considerably higher fluorescence quantum yields than the neutral precursor. These properties facilitated the design of a new nonerasable 3D fluorescence readout (permanent or write-once read-many, WORM) system, which is comprised of a switch-on fluorescent guaiazulene-containing chromophore 3e and commercially available iodonium photo-acid generator (PAG) in thin polymethyl methacrylate (PMMA) films. Scheme 1. Syntheses of 4-styrylguaiazulenes 3a-l.Reagents and conditions: (a) benzaldehyde 2a, method F, 54%; (b) 4-bromobenzaldehyde 2b, method G, 48%; (c) 4-(hexyloxy)benzaldehyde 2c, method G, 43%; (d) 4-(phenylthio)benzaldehyde 2d, method E, 35%; (e) 7-bromo-9,9-dihexyl-9H-fluorene-2carbaldehyde 2e, method F, 34%; (f) pyrene-1-carbaldehyde 2f, method E, 70%; (g) i. (b); ii. 3b, Pd(PPh 3 ) 2 Cl 2 , CuI, K 2 CO 3 , THF, 32%; (h) furan-2-carbaldehyde 2g, method G, 67%; thiophene-2carbaldehyde 2h, method G, 66%; 1-hexyl-1H-pyrrole-2-carbaldehyde 2i, method E, 71%; 1-ethyl-1Hindole-3-carbaldehyde 2j, method F, 48%; 9-ethyl-9H-carbazole-3-carbaldehyde 2k, method E, 75%. Color represents the different series compared in this work: 3a-d, 3e-g, 3h-j, and 3j-l.

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“…[23][24][25] The unique photophysical properties of azulene arise from a dissimilar distribution of electron density between the HOMO and LUMO leading to a relatively small electron repulsion energy in the fi rst excited singlet state. [26][27][28][29] Responsive materials that exhibit dramatic changes in optical properties upon the introduction of external stimuli are promising for a number of applications including sensing technologies. [26][27][28][29] Responsive materials that exhibit dramatic changes in optical properties upon the introduction of external stimuli are promising for a number of applications including sensing technologies.…”

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confidence: 99%

Modulating the Properties of Azulene‐Containing Polymers through Controlled Incorporation of Regioisomers

Tsurui

Murai

et al. 2014

Adv Funct Materials

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wileyonlinelibrary.comits constitutional isomer, naphthalene, azulene is a bright blue compound that exhibits large dipolar character (1.08 D) due to resonance delocalization that results in an electron-rich 5-membered ring and an electron-poor 7-membered ring. [23][24][25] The unique photophysical properties of azulene arise from a dissimilar distribution of electron density between the HOMO and LUMO leading to a relatively small electron repulsion energy in the fi rst excited singlet state. [ 25 ] These attributes, coupled with its stimuli-responsive behavior in acidic environments, make azulene a promising building block for the construction of new conjugated polymers with unique properties. [26][27][28][29] Responsive materials that exhibit dramatic changes in optical properties upon the introduction of external stimuli are promising for a number of applications including sensing technologies. [30][31][32] In the case of azulene-containing materials, protonation leads to the formation of a stable tropylium cation with signifi cantly different spectroscopic properties than the neutral species. [33][34][35][36] Despite its potential, most materials incorporating azulene as a building block have been limited to functionalization by various electrophilic transformations, leading to oligomers and polymers with the azulene nucleus connected exclusively through the 5-membered ring (1,3-connectivity). [37][38][39][40][41][42][43] We recently demonstrated that azulene-based materials connected through the electron-poor 7-membered ring (4,7-connectivity) exhibit unique properties, in part due to the conservation of π-conjugation after protonation. [ 44,45 ] Building on these fi ndings, the combination of both the 1,3-and 4,7-regioisomers of azulene could have important implications for materials design. In analogy to random D-A copolymers that comprise multiple types of randomly distributed donor and/or acceptor units, [ 13,[46][47][48][49][50][51][52] we hypothesized that conjugated polymers with tunable electronic properties could be accessed by incorporation of different regioisomeric azulene building blocks in which their connectivity (electron-rich or electron-poor 5-and 7-membered rings) is varied along the polymer chain.Herein, we describe the synthesis and evaluation of a series of random copolymers incorporating the azulene building block with varying ratios of 1,3-and 4,7-connectivity. Both bithiophene and fl uorene comonomers were investigated leading to two new libraries of random conjugated copolymers. Signifi cantly, we demonstrate that the optoelectronic properties Two libraries of random conjugated polymers are presented that incorporate varying ratios of regioisomeric azulene units connected via the 5-membered or 7-membered ring in combination with bithiophene or fl uorene comonomers. It is demonstrated that the optoelectronic and stimuli-responsive properties of the materials can be systematically modulated by tuning the relative percentage of each azulene building block in the polymer backbone. Signi...

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Modulating structure and properties in organic chromophores: influence of azulene as a building block

Abstract: The properties of isomeric azulene derivatives, substituted through the 5-membered ring, were examined using a combination of experimentation and theoretical calculations for a series of well-defined electroactive oligomers.

Cited by 79 publications

References 71 publications

Palladium‐Catalyzed Direct Arylation of Azulene Based on Regioselective C−H Bond Activation

Palladium‐Catalyzed Direct Arylation of Azulene Based on Regioselective C−H Bond Activation

Chromophoric materials derived from a natural azulene: syntheses, halochromism and one-photon and two-photon microlithography

Modulating the Properties of Azulene‐Containing Polymers through Controlled Incorporation of Regioisomers

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