Irreversible Thermochromism in Organic Salts of Sulfonated Anils,Crystal Growth & Design

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Irreversible Thermochromism in Organic Salts of Sulfonated Anils
Crystal Growth & Design ( IF 3.2 ) Pub Date : 2020-04-30 , DOI: 10.1021/acs.cgd.0c00188
Aijaz A. Dar ₁ , Arshid A. Ganie ₁

Affiliation

Condensation of p-amino benzenesulfonic acids with salicylaldehyde and o-vanillin and that of o-aminobenzenesulfonic acid with o-vanillin via mechanochemical grinding followed by heating under reflux yielded 4-[(2-hydroxy-benzylidene)-amino]-benzenesulfonic acid [4-SA-BA-2H] (1a), 4-[(2-hydroxy-3-methoxy-benzylidene)-amino]-benzenesulfonic acid [4-SA-oV-2H] (2a), and 2-[(2-hydroxy-3-methoxy-benzylidene)-amino]-benzenesulfonic acid [2-SA-oV-2H] (3a), respectively. Anticipating the formation of sulfonate···pyridinium supramolecular synthon, organic salts [(4,4′-BPY-2H)²⁺(4-SA-BA-H)^̅₂^–] (1), [(4,4′-BPY-2H)²⁺ (4-SA-oV-H)̅₂^–·4H₂O] (2), and [(4,4′-BPY-2H)²⁺(2-SA-oV-H)̅₂^–·2H₂O] (3) have been obtained by in situ as well as postsynthetic reaction of 1a–3a with 4,4′-bipyridine. Crystallographic investigations of the molecular salts reveal intriguing structural features and indicate the ubiquitous formation of hydroxylate···pyridinium interactions over otherwise robust sulfonate···pyridinium synthons when the hydroxyl group has an adjacent methoxy group. 1 crystallizes as an anhydrous salt with direct charge-assisted sulfonate···pyridinium interactions between crystal formers forming two-dimensional layers which π-interlock to form a rare three-dimensional yellow solid. Crystal formers in hydrated salts 2 and 3 associate through ionic hydroxylate···pyridinium interactions instead of anticipated sulfonate···pyridinium synthons. The organosulfonate ions in 2 and 3 associate with the help of octameric and tetrameric water clusters into two-dimensional and one-dimensional assemblies, respectively, which are further bridged by bis-pyridinium ions into three-dimensional colored ionic solids. The enhanced optical behavior of 1–3 on formation from 1a–3a is investigated through diffuse reflectance studies. Schiff base 1a and its salt 1 exhibit redshift on heating, both 2a and 2, as well as 3a do not respond notably to heat, while as 3 undergoes a remarkable blue shift on heating. Optical studies vis-à-vis crystallographic investigations rule out the conventional and general mechanism, i.e., enol ↔ cis–keto isomerization and instead strongly indicate packing changes to be the cause of irreversible thermochromism observed in 1 and 3. Furthermore, the resultant molecular salts exhibit significant thermal and chemical stability, and their formation is also substantiated by spectroscopic and analytical methods.

中文翻译：

磺化茴香有机盐中的不可逆热致变色

通过机械化学研磨，然后加热回流，将对氨基苯磺酸与水杨醛和邻香兰素进行缩合，对邻氨基苯磺酸与邻香兰素进行缩合，然后在回流下加热，得到4-[（（2-羟基-亚苄基）-氨基]-苯磺酸[ 4-SA-BA-2H]（1a），4-[（（2-羟基-3-甲氧基-亚苄基）-氨基]-苯磺酸[4-SA-oV-2H]（2a）和2-[（ 2-羟基-3-甲氧基-亚苄基）-氨基]-苯磺酸[2-SA-oV-2H]（3a）。预测的形成磺酸盐...吡啶鎓的超分子合成子，有机盐[（4,4'- BPY-2H）²⁺（4-SA-BA-H）^̅₂^-]（1），[（4,4'- BPY-2H）²⁺（4-SA-OV-H）̅ ₂^- ·4H ₂ O]（2）和[（4,4'- BPY-2H ）²⁺（2-SA-OV-H）̅ ₂^- ·2H ₂ O]（3）已经被通过原位以及将合成后反应获得1A -图3a与4,4'-联吡啶。分子盐的晶体学研究揭示了有趣的结构特征，并表明当羟基具有相邻的甲氧基时，在坚固的磺酸盐···吡啶鎓合成子上普遍形成了羟基化物···吡啶鎓相互作用。1个通过直接电荷辅助的磺酸盐···吡啶鎓相互作用形成无水盐，形成形成二维层的π互锁，形成稀有的三维黄色固体。水合盐2和3中的晶体形成剂通过离子羟基化···吡啶相互作用而不是预期的磺酸盐···吡啶合成子缔合。2和3中的有机磺酸根离子借助八聚体和四聚体水簇分别缔结成二维和一维组件，再由双吡啶离子桥接成三维有色离子固体。的增强的光学行为1 - 3通过漫反射研究，研究了从1a到3a的地层形成情况。席夫碱1a及其盐1在加热时表现出红移，2a和2以及3a对加热均无明显响应，而3则在加热时发生明显的蓝移。光学研究相对于晶体学研究排除了常规和通用机理，即烯醇↔顺式-酮异构化，而是强烈表明堆积变化是在1和3中观察到的不可逆热致变色的原因。。此外，所得的分子盐表现出显着的热和化学稳定性，并且其形成也通过光谱和分析方法得以证实。

更新日期：2020-04-30

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