Search

Conjugated small molecules bearing the cyano group were reviewed. These organic compounds are extensively used as active layers of solar cells and light-emitting diodes as well as materials with high second- and third-order nonlinearities. Typical organic light conversion agents are also based on CN-capped π-conjugated scaffolds that, in addition, are also increasingly popular for building various organic sensors and probes. More recently, cyanoarenes and dicyanopyrazines were identified as efficient photoredox catalysts. Fundamental structure–property relationships of CN-capped molecules used across the aforementioned areas were elucidated and discussed. The cyano group possessing electron-withdrawing character and linear arrangement is capable of significantly altering electronic and optical properties, and supramolecular arrangement. Hence, extensive property tuning/regulation through the CN group has been demonstrated. [ABSTRACT FROM AUTHOR]

Developing new organic chromophores with a large electro-optic coefficient (r33) is highly desirable for fabricating electro-optic (EO) materials. Building on the fact that the 1,1,7,7-tetramethyl julolidine fused furan ring is a good electron donor and lengthening the π-bridge of a chromophore with a five-membered heterocycle ring could lead to the improvement of r33. Here we design and synthesize two new chromophores C1 and C2 by using a 1,1,7,7-tetramethyl julolidine fused furan ring as the electron donor and 2-(3-cyano-4,5,5-trimethyl-5H-furan-2-ylidene)-malonitrile (TCF) as the acceptor, but with two different π-bridges (furan-vinylene and thiophene-vinylene accordingly). When doping C1 or C2 into PMMA with a loading density of 20 wt%, the poled films containing C1 or C2 exhibited an r33 value of 75 pm V−1 and 94 pm V−1, respectively. When compared with chromophore C3 (an ene unit as the π-bridge, r33 = 52 pm V−1), an enhanced r33 of C1 and C2 was achieved due to the introduction of a heterocycle ring into the π-bridge. This work uncovers the influence of the heterocycle ring on the julolidine fused furan based chromophore's physical and chemical properties and demonstrates that the new chromophores are a promising candidate for EO material application. [ABSTRACT FROM AUTHOR]

A series of chromophores J1–J4 have been synthesized based on julolidine donors modified with different rigid steric hindrance groups. Compared with the chromophore (J1) without the isolation group, chromophores J2, J3 and J4 show better stability. Structural analysis and photophysical property measurements were carried out to compare the molecular mobility and steric hindrance effect of the different donor-modified chromophores. All of these chromophores with isolation groups showed superb thermal stabilities with high thermal decomposition temperatures above 250 °C. Furthermore, with rigid steric hindrance, chromophores J3 and J4 showed more enhanced thermal stabilities with thermal decomposition temperatures of 269 °C and 275 °C, respectively. Density functional theory was used to calculate the hyperpolarizability (β), and the high molecular hyperpolarizability of these chromophores can be effectively translated into large electro-optic coefficients. The electro-optic coefficients of poled films containing 20 wt% of these new chromophores doped in amorphous polycarbonate were 127, 266 and 209 pm V−1 at 1310 nm for chromophores J1–J3, respectively, while the film containing chromophore J4 showed the largest r33 value of only 97 pm V−1 at 25 wt%. These results indicated that the introduced isolation group can reduce intermolecular electrostatic interactions, thus enhancing the macroscopic electro-optic activity, while the size of the isolation group should be suitable. [ABSTRACT FROM AUTHOR]

Three novel second order nonlinear optical (NLO) chromophores based on julolidinyl donors and tricyanofuran (TCF) acceptors linked together via modified polyene π-conjugation with rigid benzene derivative steric hindrance groups (chromophore CL1 and CL2) or unmodified polyene π-conjugation (chromophores CL) moieties as the bridges have been synthesized in good overall yields and systematically characterized. Density functional theory (DFT) was used to calculate the HOMO–LUMO energy gaps and first-order hyperpolarizability (β) of these chromophores. Besides, to determine the redox properties of these chromophores, cyclic voltammetry (CV) experiments were performed. Compared with CL, after introducing benzene derivative steric hindrance groups into the bridge, chromophores CL1 and CL2 had good thermal stabilities with high thermal decomposition temperatures which were 32 °C and 24 °C higher than chromophore CL, respectively. Most importantly, the introduction of rigid steric hindrance groups can effectively reduce dipole–dipole interactions to translate their relatively small β values into bulk high EO activities. By doping chromophores CL, CL1 and CL2 with a high loading of 45 wt% in APC, EO coefficients (r33) of up to 121, 197 and 202 pm V−1 at 1310 nm can be achieved, respectively. The r33 values of new chromophores CL1 and CL2 were about 1.6 times of chromophore CL. The high r33 value, good thermal stability and high yield suggest the potential use of the new chromophores in an nonlinear optical area. [ABSTRACT FROM AUTHOR]

A series of Y-shaped chromophores A1, A2, B1 and B2 based on the same thiophene π-conjugation and tricyanofuran acceptor (TCF) but with different donors (modified phenothiazine and triphenylamine) have been synthesized and systematically investigated in this paper. Density functional theory (DFT) was used to calculate the HOMO–LUMO energy gaps and first-order hyperpolarizability (β) of these chromophores. These chromophores showed excellent thermal stability with their decomposition temperatures all above 270 °C. Most importantly, the high molecular hyperpolarizability of these chromophores can be effectively translated into large electro-optic (EO) coefficients (r33) in poled polymers. The doped film-C containing 25 wt% chromophore B1 displayed an r33 value of 72 pm V−1 at 1310 nm, and the doped film-D containing B2 showed a value of 95 pm V−1 at a concentration of 25 wt%. These values are all much higher than the traditional FTC chromophore (39 pm V−1). High r33 values indicated that the special Y structure can reduce intermolecular electrostatic interactions and thus enhance the macroscopic EO activity. These properties, together with the good solubility, suggest the potential use of these new chromophores as materials for advanced devices. [ABSTRACT FROM AUTHOR]

A series of chromophores FTC, L1 and L2 have been synthesized based on three different types of electron donors, including diethylaminophenyl, tetrahydroquinolinyl and N-(4-dimethylaminophenyl) tetrahydroquinolinyl groups respectively, with the same thiophene bridges and strong tricyanovinyldihydrofuran (TCF) acceptors. In particular, the donor part of the chromophore L2 was modified with an additional donor N-(4-dimethylaminophenyl) substituent, resulting in enhanced thermal stability and electro-optic activity. Cyclic voltammetry measurements showed that chromophore L2 had a smaller energy gap than chromophore L1 due to the additional donor. Moreover, density functional theory calculations suggested that the molecular quadratic hyperpolarizability (μβ) value of chromophore L2 is 29% and 44% larger than that of chromophores L1 and FTC, respectively. The doped film containing the chromophore L2 showed an r33 value of 100 pm V−1 at the concentration of 25 wt% which is much higher than the EO activity of the chromophore L1 (57 pm V−1) and two times higher than that of the traditional chromophore FTC (39 pm V−1). [ABSTRACT FROM AUTHOR]

A series of chromophores T1–T3 based on the same thiophene π-conjugation and tricyanofuran acceptor (TCF) but with different heteroatoms in the triarylaminophenyl (TAA) donors have been synthesized and systematically investigated in this study. Density functional theory (DFT) was used to calculate the HOMO–LUMO energy gaps and first-order hyperpolarizability (β) of these chromophores. Moreover, to determine the redox properties of these chromophores, cyclic voltammetry (CV) experiments were performed. After introducing the heteroatom to the benzene ring of the TAA donor, reduced energy gaps of 1.28 and 0.84 eV were obtained for chromophores T2 and T3, respectively, which was much lower than for chromophore T1 (ΔE = 1.46 eV). These chromophores showed excellent thermal stability with their decomposition temperatures all above 280 °C. Compared with results obtained from the chromophore without the heteroatom (T1), these new chromophores show better intramolecular charge-transfer (ICT) absorption. Most importantly, the high molecular hyperpolarizability (β) of these chromophores can be effectively translated into large electro-optic (EO) coefficients (r33) in the poled polymers. The electro-optic coefficient of poled films containing 25 wt% of these new chromophores doped in amorphous polycarbonate (APC) afforded values of 16, 58 and 95 pm V−1 at 1310 nm for chromophores T1–T3, respectively. High r33 values indicated that introducing heteroatom to the benzene ring of the TAA donor can efficiently improve the electron-donating ability, which improves the hyperpolarizability (β). The long-chain on the benzene ring of the TAA donor, acting as the isolation group, may reduce intermolecular electrostatic interactions, thus enhancing the macroscopic EO activity. These properties, together with the good solubility, suggest the potential use of these new chromophores as advanced material devices. [ABSTRACT FROM AUTHOR]

Two novel chromophores y1 and y2 based on the same double donors and the tricyanofuran acceptor linked together via the modified thiophene π-conjugation have been synthesized and systematically investigated. Density functional theory was used to calculate the energy gaps and first-order hyperpolarizability (β) of the two chromophores. Besides, cyclic voltammetry (CV) experiments were performed to determine the different redox properties. The electro-optic coefficient of poled films containing 25 wt% of chromophore y1 and y2 doped in amorphous polycarbonate afforded values of 163 and 105 pm V−1 at 1310 nm, respectively. The obvious different results indicated that the position of the oxygen atom on the thiophene ring is essential to the linear and nonlinear optical properties, with the best results obtained when the alkoxy group was closer to the donor moiety. These results are useful in designing the nonlinear optical materials and will provide new guidance for the future research. [ABSTRACT FROM AUTHOR]

A new chromophore HK containing the cis,cis-1,7-diethoxy-3-isopropyljulolidine group as a novel electron-donor, thiophene as a π-conjugated bridge and a tricyanofuran (TCF) acceptor has been synthesized and systematically investigated in this paper. Its corresponding chromophore FTC using 4-(diethyl amino)benzyl as the electron donor group was also prepared for comparison. This is the first time that the cis,cis-1,7-diethoxy-3-isopropyljulolidine group was introduced into NLO materials. Density functional theory (DFT) was used to calculate the HOMO–LUMO energy gap and first-order hyperpolarizability (β) of the new chromophore. The HOMO–LUMO gap was also investigated by cyclic voltammetry (CV). Upon using the cis,cis-1,7-diethoxy-3-isopropyljulolidine group as the donor, a reduced energy gap of 1.007 eV was obtained compared with chromophore FTC (ΔE = 1.529 eV). The high molecular hyperpolarizability of the new chromophore can be effectively translated into large electro-optic (EO) coefficients (r33) in poled polymers. The doped films containing the new chromophore HK showed a value of 72 pm V−1 at the concentration of 25 wt% at 1310 nm. This value is almost two times higher than the EO activity of the usually reported traditional (N,N-diethyl) aniline nonlinear optical (NLO) chromophore FTC. High r33 values indicated that the new julolidine donor can efficiently improve the electron-donating ability and reduce intermolecular electrostatic interactions, thus enhancing the macroscopic EO activity. These properties, together with good solubility, suggest the potential use of the new chromophore in advanced materials devices. [ABSTRACT FROM AUTHOR]

New Y-type chromophores FTC-yh1 and FTC-yh2 containing bis(N,N-diethyl)aniline as a novel electron-donor, thiophene as a π-conjugated bridge and tricyanofuran (TCF) as an acceptor have been synthesized and systematically investigated in this paper. Density functional theory (DFT) was used to calculate the HOMO–LUMO energy gaps and first-order hyperpolarizability (β) of these chromophores. These chromophores showed better thermal stability with their decomposition temperatures all above 240 °C. Most importantly, the high molecular hyperpolarizability of these chromophores can be effectively translated into large electro-optic (EO) coefficients (r33) in poled polymers. The doped film-A containing 25 wt% chromophore FTC-yh1 displayed a value of 149 pm V−1 at 1310 nm, and the doped film-B containing FTC-yh2 showed a value of 143 pm V−1 at the concentration of 25 wt%. These values are almost four times higher than the EO activity of usually reported traditional single (N,N-diethyl)aniline nonlinear optical (NLO) chromophores FTC. High r33 values indicated that the double donors of the bis(N,N-diethyl)aniline unit can efficiently improve the electron-donating ability and reduce intermolecular electrostatic interactions, thus enhancing the macroscopic EO activity. These properties, together with the good solubility, suggest the potential use of the new chromophores as advanced material devices. [ABSTRACT FROM AUTHOR]

Typical small organic dyes exhibit excellent UV absorption capabilities and are commonly used as additives to shield plastic films from photoaging. However, their tendency to decompose easily and migrate rapidly within a polymer matrix limits their service life. Herein we prepared g-C 3 N 4 nanosheets and fabricated g-C 3 N 4 /PBAT films to investigate the effects of g-C 3 N 4 on UV shielding and plasticizing of a biodegradable PBAT film. Photophysical characterizations revealed that an improved UV light barrier performance was achieved on g-C 3 N 4 /PBAT films compared to pure PBAT. Furthermore, the photoaging results show that g-C 3 N 4 can stably exist in the PBAT matrix, enabling the aged g-C 3 N 4 /PBAT films to maintain their effective UV shielding ability, whereas the aged benzophenone (UV-0)/PBAT film shows a substantial decrease in UV light absorption due to the photodecomposition of UV-0. Additionally, g-C 3 N 4 acted as a reinforcing material for PBAT, as evidenced by the approximately 1.5-fold increase in longitudinal tear strength and 1.6-fold increase in tensile strength of g-C 3 N 4 /PBAT films compared to pure PBAT. Remarkably, even after 100 hours of photoaging, the aged g-C 3 N 4 /PBAT films retained their favorable mechanical properties. This study highlights the potential of g-C 3 N 4 as a new type of UV shield additive for future practical applications in protecting biodegradable plastic from photoaging., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A new diene-conjugated chromophore WJ1 was synthesized with high yield of 36% through an H-bonding induced Vilsmeier reaction. By simple guest-host doping, a large electro-optic efficiency of 337 pm V(-1) at 1310 nm and excellent temporal stability at 75 °C have been achieved in poled films of WJ1/APC with a high loading density of 40 wt%.