1,2-Bis(2-bromophenyl)ethynes: The influence of 5′-methoxy and 5′-difluoromethoxy groups on the electronic properties and crucial bond lengths

IF 2.7 3区 化学 Q2 CHEMISTRY, INORGANIC & NUCLEAR
David H.I. Maier, Frederick J.F. Jacobs, Barend C.B. Bezuidenhoudt, Alice Brink, Charlene Marais
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Abstract

The effect of methoxy and difluoromethoxy groups para to the bromo substituent of 1,2-bis(2-bromophenyl)ethynes on the conformation of the molecule and the properties of the CC and CBr bonds was investigated by single crystal X-ray diffractometry and Nuclear Magnetic Resonance spectroscopy. The difluoromethoxy and methoxy groups both activated the ortho positions, as was evident from the shielding of both the proton and carbon atoms at these positions in NMR experiments. The C6-C≡C-C6 system in 1,2-bis(2-bromophenyl)ethyne, 1,2-bis(2-bromo-5-(difluoromethoxy)phenyl)ethyne, 1,2-bis(2-bromo-5-methoxyphenyl)ethyne and 1-bromo-2-((2-bromophenyl)ethynyl)-4-methoxybenzene is in effect coplanar, with the dihedral angle between the two ring planes ranging from 0° to 5.8°. Substitution has little effect on the electronic properties of the triple bond, as was evident from the similar 13C NMR spectroscopy chemical shifts and crystallographic bond distances. This is also reflected in the similar angles at the sp- centra, which deviate only slightly from linearity (177.3(2) – 179.6(1)°). The OCF2H substituent resulted in a small contraction of the CBr bond and OCH3 in a slight elongation. The bromo-bearing carbon was shielded with 3.8 ppm by the OCF2H group and by more than 9 ppm relative to an H atom by the OCH3 group in 13C NMR spectroscopy experiments.
1,2-双(2-溴苯基)乙炔:5 ' -甲氧基和5 ' -二氟甲氧基对电子性质和关键键长的影响
采用单晶x射线衍射仪和核磁共振波谱仪研究了1,2-双(2-溴苯基)乙炔中对溴取代基的甲氧基和二氟甲氧基对分子构象和CC、CBr键性质的影响。二氟甲氧基和甲氧基都激活了邻位,这一点从核磁共振实验中质子和碳原子在这些位置的屏蔽中可以明显看出。1,2-二(2-溴苯基)乙炔、1,2-二(2-溴-5-(二氟甲氧基)苯基)乙炔、1,2-二(2-溴-5-甲氧基)乙炔和1-溴-2-((2-溴苯基)乙基)-4-甲氧基苯中的C6-C≡C-C6体系实际上是共面的,两个环面之间的二面角为0°至5.8°。取代对三键的电子性质影响不大,从类似的13C核磁共振光谱化学位移和晶体键距离可以看出。这也反映在sp-中心点的相似角度上,该角度仅略微偏离线性(177.3(2)- 179.6(1)°)。OCF2H取代基导致CBr键轻微收缩,OCH3键轻微伸长。在13C核磁共振光谱实验中,含溴碳被OCF2H基团屏蔽了3.8 ppm,被OCH3基团屏蔽了9 ppm以上。
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来源期刊
Inorganica Chimica Acta
Inorganica Chimica Acta 化学-无机化学与核化学
CiteScore
6.00
自引率
3.60%
发文量
440
审稿时长
35 days
期刊介绍: Inorganica Chimica Acta is an established international forum for all aspects of advanced Inorganic Chemistry. Original papers of high scientific level and interest are published in the form of Articles and Reviews. Topics covered include: • chemistry of the main group elements and the d- and f-block metals, including the synthesis, characterization and reactivity of coordination, organometallic, biomimetic, supramolecular coordination compounds, including associated computational studies; • synthesis, physico-chemical properties, applications of molecule-based nano-scaled clusters and nanomaterials designed using the principles of coordination chemistry, as well as coordination polymers (CPs), metal-organic frameworks (MOFs), metal-organic polyhedra (MPOs); • reaction mechanisms and physico-chemical investigations computational studies of metalloenzymes and their models; • applications of inorganic compounds, metallodrugs and molecule-based materials. Papers composed primarily of structural reports will typically not be considered for publication.
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