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Syntheses of Chalcone-Type Chlorophyll Derivatives Possessing a Bacteriochlorin, Chlorin, or Porphyrin <i>π</i> -System and Their Optical Properties
摘要： C3-(Trans-arylethenyl)carbonylated chlorophyll derivatives possessing a bacteriochlorin or chlorin π-system were synthesized by cross-aldol (Claisen-Schmidt) condensation of methyl pyrobacteriopheophorbide-a or 3-acetyl-3-devinyl-pyropheophorbide-a bearing the C3-acetyl group with p-(un)substituted benzaldehydes under basic conditions. The corresponding porphyrin-type chlorophyll derivatives were prepared by the oxidation (17,18-didehydrogenation) of the chlorin-type. Their Qy absorption and fluorescence emission maxima in dichloromethane correlated well with Hammett substituent constants of the p-substituents. Several electron-withdrawing p-substituents suppressed the emission due to photoinduced electron transfer quenching in a molecule. The substitution sensitivities for their maxima and fluorescence quantum yields decreased in the order of bacteriochlorin-, chlorin-, and porphyrin-type derivatives.
关键词： Chlorophyll derivatives,Optical properties,Bacteriochlorin,Cross-aldol condensation,Hammett substituent constants,Porphyrin,Chlorin
更新于2025-09-23 15:21:01
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[ACS Symposium Series] Raman Spectroscopy in the Undergraduate Curriculum Volume 1305 || Connecting Organic and Physical Chemistry Students with Raman Spectroscopy
摘要： The profile of Raman spectroscopy may be elevated in the undergraduate chemistry curriculum by intentionally tying together students’ experiences in the organic and physical chemistry laboratories. In this way the valuable role Raman spectroscopy can play in structure elucidation is highlighted. The Committee on Professional Training of the American Chemical Society includes the category of optical molecular spectroscopy (e.g., IR, UV-Vis, Raman, and fluorescence spectroscopies) as an option in the panel of instruments required for certification. To the authors’ knowledge there are no Raman spectroscopy experiments that build directly on the analysis of compounds synthesized by students in a prior course for the intended purpose of scaffolding the curriculum. This chapter highlights the roles Raman spectroscopy may play in the determination of molecular structure when used in conjunction with other, more common techniques. Indeed, direct comparison to infrared spectroscopy holds the potential to reinforce that technique and its applications while introducing the study of Raman spectra. A set of three reaction products from electrophilic aromatic substitution, Diels-Alder, and aldol condensation (this including site-specific deuteration) is explored. All of these reactions are currently part of the organic chemistry curriculum. By combining analyses performed in organic chemistry with new laboratories written for the physical chemistry laboratory the authors hope to impress upon undergraduates the value of Raman spectroscopy in a context that builds on their previous experiences with other molecular spectroscopy methods.
关键词： structure elucidation,undergraduate chemistry curriculum,electrophilic aromatic substitution,Diels-Alder reaction,Raman spectroscopy,infrared spectroscopy,deuteration,physical chemistry,aldol condensation,organic chemistry
更新于2025-09-04 15:30:14
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Scalable Synthesis of Naphthothiophene and Benzodithiophene Scaffolds as π-Conjugated Synthons for Organic Materials
摘要： The synthesis on a gram-scale and the full characterization of naphtho[1,2-b]thiophene and benzo[1,2-b:6,5-b']dithiophene 4-carboxylate esters bearing 2-octyldodecyl side chains, and their stannylated and brominated derivatives, suitable for their insertion into π-conjugated polymers is described. The fully soluble and processable synthons are obtained through a cascade sequence of reactions, namely direct arylation and cross aldol condensation, which create an effective pathway for the annulation and π-extension of suitable, commercially available reagents. The newly reported synthesis are compared, whenever possible, using ‘green chemistry metrics’ with literature synthesis, showing dramatic improvements.
关键词： cross aldol condensation,annulation,heterocycles,organic materials,direct arylation
更新于2025-09-04 15:30:14