Three-Dimensional Hexagonal Structures from a Novel Self-Complementary Molecular Building Block

Nitrilotri(methylphosphonic acid), 1H6, exists as a zwitter ion in its pure form and reveals a complex
three-dimensional structure with no predictable structural patterns. However, when acid 1H6 is reacted with
1,7-phenanthroline, 2, 1,10-phenanthroline, 3, acridine, 6, and tripropylamine, 8, in a 1:1 molar ratio,
monodeprotonation of 1H6 triggers a prototypal self-complementary 3D hexagonal architecture in complexes
9 (1H5·H·2H2O), 10 (1H5·3H), 11 (1·5H)·(5)0.5, and 12 (1·8H). The networks are stabilized by very strong
ionic hydrogen bonds and offer a viable new strategy for the design of stable and predictable 3D open organic
networks. However, monodeprotonation of acid 1H6 with quinoline, 6, does not lead to the expected open
hexagonal structure in 13 (1·6H) as quinolinium cations cannot effectively fill the void space if open hexagonal
open structures were formed. The unique three-dimensional connectivity of these open networks does not
permit interweaving, and template effects play a critical role in the formation of open structures. The double
deprotonation of acid 1H6 with amines 2, 4,7-phenanthroline, 3, and diisopropylamine, 7, leads to the formation
of complexes 14 (1H4·(2H)2·2H2O), 15 (1H4·(4H)2·5H2O), and 16 (1H4·7H) with one-dimensional chain
structures only. Crystal structures of 9−16 together indicate the importance of the ionic hydrogen bond donor:acceptor ratio in determining 3D hexagonal network formation. Further, the proton transfer from acid 1H6 to
phenanthrolines influences the absorption properties of 9, but has no effect on 10. 1,7-Phenanthroline (mp 80
°C) changes its color from pale yellow to deep orange-red upon protonation and exhibits stability up to 325
°C. These results bring out a new concept, that we may be able to control absorption properties and heat
stability of pigments/colorants by encapsulating different structural forms into a rigid three-dimensional host
matrix by optimizing hydrogen bond properties.

次氨基三(甲基膦酸)（1H6）在纯态下以两性离子形式存在，其三维结构复杂且无规可循，无法预测其结构模式。然而，当酸1H6分别与1,7-菲咯啉（2）、1,10-菲咯啉（3）、吖啶（6）以及三丙胺（8）以1:1的摩尔比反应时，1H6的单去质子化会诱导形成原型自互补的三维六边形结构，生成配合物9（1H5·H·2H2O）、10（1H5·3H）、11（1·5H）·(5)0.5以及12（1·8H）。该类网络通过极强的离子氢键得以稳定，为设计稳定且可预测的三维开放有机网络提供了切实可行的新策略。不过，当酸1H6与喹啉（6）发生单去质子化反应时，并未在配合物13（1·6H）中得到预期的开放六边形结构——这是因为若形成开放六边形结构，喹啉鎓阳离子无法有效填充其空隙空间。这类开放网络独特的三维连接方式使其无法发生交织，而模板效应对开放结构的形成起到关键作用。当酸1H6与胺类（2）、4,7-菲咯啉（3）以及二异丙基胺（7）发生双去质子化反应时，仅会生成具有一维链状结构的配合物14（1H4·(2H)2·2H2O）、15（1H4·(4H)2·5H2O）以及16（1H4·7H）。配合物9至16的晶体结构共同表明，离子氢键给体-受体比例对三维六边形网络的形成至关重要。此外，酸1H6向菲咯啉类的质子转移会影响配合物9的吸收性能，但对配合物10无影响。1,7-菲咯啉的熔点为80℃，质子化后其颜色会由浅黄色变为深橙红色，且热稳定性可达325℃。上述研究结果提出了一个全新的概念：通过优化氢键性质，将不同结构形式包封于刚性三维主体基质中，我们便可调控颜料/着色剂的吸收性能与热稳定性。