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Organometallic Compounds as Heterogeneous Catalysts
Published in Varun Rawat, Anirban Das, Chandra Mohan Srivastava, Heterogeneous Catalysis in Organic Transformations, 2022
Garima Sachdeva, Monu Verma, Varun Rawat, Ved Prakash Verma, Manish Srivastava, Sudesh Kumar, Singh Vanshika
1,4-Diketones are significant organic scaffolds used as precursors for the preparation of several heterocyclic compounds. Due to this reason, many protocols have been developed for their synthesis. An effective and novel methodology was reported by Varea et al. for the synthesis of disubstituted 1,4-diketones from squaric acid derivatives. The protocol involves the addition of organolithium compound on squaric acid at room temperature followed by hydrolysis (Figure 4.15) [31].
Theory Study and Present CT Trend of Organic Charge Transfer Complexes
Published in Atsushi Nagai, Koji Takagi, Conjugated Objects, 2017
Atsushi Nagai, Daniel J. Siegwart
Recently organic complexes with electron donor (D) and electron acceptor (A) moieties have emerged as promising candidates for advanced mechanochromic materials due to their intramolecular CT capability This endows the materials with charge ordering, spin density waves (SDWs), spin‐Peierls ground state, and superconductivity 17 Aromatic molecules, such as coronene, are typical examples of π‐electron systems able to donate electrons, depending on their ionization potential I. As a typical example, 7,7,8,8‐tetracyanoquinodimethane (TCNQ) can be easily reduced to form the open‐shell electron radical anion TCN Q when it comes into contact with electron donors. Recently a three‐component system comprising two differentbenzenoid hydrocarbons together with one molecule of TCNQ was reported.18 The pyreneTCNQ complex was synthesized with a molecular ratio of 1:1 in toluene under refluxing conditions. Notably the compound crystallized in a monoclinic system, with a space group of P21/n with half of the molecules of pyrene and TCNQ as the asymmetric part of the unit cell. The pyrene moiety is tilted with respect to the TCNQ along the stacks, with an angle between mean planes of 6o (Fig. 14.2). If this principle could be introduced into an oligomer ore polymer chain backbone, a force‐ sensitive CT complex as the chemical unit (mechanophore) would be linked into the polymer and oligomer backbones. Mechanical loading would then drive conversion of the mechanophore to a new chemical species. Therefore, we expect the possibility of completely alternating stacking for the CT complex between pyrene and TCNQ using mechanical grinding. This is to say the mechanochromism 19 phenomenon will be observed, which is characterized by changes in color (absorption) and/or luminescence as a result of mechanical grinding or pressing of a sample in the solid state. Accordingly the mechanical grinding of pyreneTCNQ complexes in the solid state would lead to a much higher increase of high CT complex absorption and the color of the grinded solid will change. To create the system described above utilized the simple structure of squaramide, which is typically synthesized via the stepwise reaction of commercially available squaric acid with amines and aromatic amines.20 The hydrogen bond donoracceptor properties of squaramide have attracted interest for various applications in supramolecular chemistry for example, as catalysts21, molecular sensors, 22 and in molecular recognition as receptors for charged guests.23 Moreover there is a growing number of bioactive squaramides involved in cancerous,24 inflammatory25 and infectious26 diseases, among others.
Construction and in-cage modification of metal-organic polyhedra based on Anderson-like polyoxovanadate clusters
Published in Journal of Coordination Chemistry, 2022
Yuhan Hou, Huiping Chen, Ting Zhang, Yaru Gong, Haiyan Zheng, Baoshan Hou, Xinlong Wang
In the past several decades, the synthesis of MOPs formed by polyoxovanadate SBUs and N- or O-containing organic ligands have attracted the attention of synthetic chemists. In 2001, the first cubic polyoxovanadate MOP using 3-connected {(VO3)3(OMe)4} and squaric acid [11] was reported by Hartl. Since then, a series of SBUs have been synthesized, such as 3-connected [V7O6(OMe)9SO4] [2], 4-connected {V4O8Cl} [12] and {V5O9Cl} [13], and 5-connected {WV5O11(SO4)6} [14]. Dozens of structurally diverse nanosized MOPs by selecting the appropriate polyoxovanadate SBUs and different ligands have been reported. In 2016, Zhang first reported a SBU with an Anderson-like conformation with a specific coordination pattern, [V6O6(OCH3)9(SO4)(COO)3]8−({V6S}) to construct metal-organic polyhedra [15]. Its triple linkage sites on the skeleton allow it to create tetrahedral VMOPs of different sizes by covalently grafting with varying dentate or trigonal ligands. Gong exploited this property to the extreme by using the long-chain bidentate ligand H2edb (4,4′-(ethyne-1,2-diyl)dibenzoic acid) to synthesize tetrahedra and pioneered to use it as a synthetic SBU to construct two interconvertible supramolecular isomers [16]. Moreover, in 2020, {V6S} SBU was also utilized to construct molecular cubes with tetradentate ligands through face-directed assembly [17]; the structures and possibilities of polyoxovanadate MOPs are significantly broadened.
Dual colorimetric and fluorescent determination of iron (III) using a novel squaraine dye
Published in Instrumentation Science & Technology, 2018
Chen Zhang, Mengyuan Wang, Yuzhe Zhang, Zhongyu Li, Song Xu
Salts of the different cations were purchased from Shanghai Chemical Reagents (China) and used without further purification. Stock solutions (10 mM) of chlorinated salts (Cr3+) and nitrate salts (Pb2+, Na+, Ni2+, Fe3+, Mg2+, K+, Zn2+, Ag+, Ca2+, Ba2+, Cu2+, Co2+, Al3+, and Cd2+) were prepared with deionized water. Squaric acid, 2,3,3-trimethylindolenine, iodoethane, 4-hydrazinobenzoic acid hydrochloride, and 3-methyl-2-butanone were purchased from energy chemical and used without further purification.
Shortwave infrared-absorbing squaraine dyes for all-organic optical upconversion devices
Published in Science and Technology of Advanced Materials, 2021
Karen Strassel, Wei-Hsu Hu, Sonja Osbild, Daniele Padula, Daniel Rentsch, Sergii Yakunin, Yevhen Shynkarenko, Maksym Kovalenko, Frank Nüesch, Roland Hany, Michael Bauer
The squaraine dyes SQ1 – SQ4 were synthesized according to an adapted procedure from literature [40]. Iminium salts 7–10 were condensed with squaric acid by refluxing in a mixture of n-butanol and toluene. Recrystallization from ethanol resulted in the corresponding dyes in yields of 42% – 69%.