Linking Hydrogen Dicarboxylate Synthons with Substituted Guanidinium Cations: Transforming Rings and Chains into Two- and Three-Dimensional Structures

Hydrogen-bonding interactions between N,N‘,N‘ ‘-trisubstituted guanidinium cations and hydrogen dicarboxylates are
explored. The extended structures of these compounds combine established structural motifs for the hydrogen carboxylate anions
with C3-symmetric guanidinium links. Both N,N‘,N‘ ‘-triisopropylguanidine (TPG) and N,N‘-diisopropyl-N‘ ‘-pentafluorophenylguanidine
(DPArG) react in 1:1 stoichiometry with oxalic acid to yield compounds that were crystallized from tetrahydrofuran (THF) to give
(TPGH)(C2O4H)(THF)0.5(1) and (DPArGH)C2O4H(THF) (2). Compound 1 displayed hydrogen oxalate dimers (

(10) motif) that
are bridged with the TPGH+ cation to yield an open three-dimensional (3-D) structure that crystallized around occluded THF. In the
case of compound 2, the targeted (DPArGH)(C2O4H) incorporated an additional hydrogen-bonded THF molecule to provide a structure
in which the -O2CCOOH anion exhibited head-to-tail chains (C(5) motif) that are cross-linked through hydrogen bonds with
[(DPArGH)(THF)]+ to yield two-dimensional (2-D) layers that stack along the c-axis. TPG also reacts stoichiometrically with succinic
(butanedioic) acid and maleic (cis-2-butenedioic) acid to produce guanidinium hydrogen dicarboxylate salts (TPGH+)(-O2CC2H4CO2H)
(3) and (TPGH+)(-O2CCHCHCO2H) (4). The primary structure of 3 combines head-to-tail hydrogen-bonded chains of monoanionic
dicarboxylic acids with chain-spanning planar TPGH+ cations to give a cross-linked ladder motif that ultimately generates a 3-D
net. In the case of 4, the hydrogen maleate anion displayed a characteristic intramolecular, low barrier hydrogen bond (LBHB) (S(7)
motif). Hydrogen bonding between planar TPGH+ and the cyclic, planar anion leads to a layered solid-state structure consisting of
a corrugated 2-D net constructed from 16- and 42-membered rings.

本研究探讨了N,N',N''-三取代胍阳离子（N,N',N''-trisubstituted guanidinium cation）与氢二羧酸根（hydrogen dicarboxylate）之间的氢键相互作用。这类化合物的扩展结构将氢羧酸根阴离子已确立的结构基元与C3对称的胍连接单元相结合。N,N',N''-三异丙基胍（TPG）与N,N'-二异丙基-N''-五氟苯基胍（DPArG）均以1:1的化学计量比与草酸反应，产物分别从四氢呋喃（THF）中结晶得到(TPGH)(C₂O₄H)(THF)₀.₅(1)与(DPArGH)C₂O₄H(THF)(2)。化合物1呈现出草酸氢根二聚体（(10)型基元），该二聚体通过与TPGH⁺阳离子桥连，形成了围绕包埋四氢呋喃的开放三维（3D）结构。对于化合物2，目标产物(DPArGH)C₂O₄H结合了一个额外的氢键合四氢呋喃分子，其结构中-O₂CCOOH阴离子呈现出头尾相连的链状结构（C(5)型基元），该链通过与[(DPArGH)(THF)]⁺阳离子的氢键作用交联，形成沿c轴堆叠的二维（2D）层状结构。TPG同样以化学计量比与琥珀酸（丁二酸）及马来酸（顺式-2-丁烯二酸）反应，得到胍类氢二羧酸盐水合物(TPGH⁺)(-O₂CC₂H₄CO₂H)(3)与(TPGH⁺)(-O₂CCH=CHCO₂H)(4)。化合物3的初级结构将单阴离子二羧酸的头尾氢键链与跨链的平面TPGH⁺阳离子相结合，形成交联梯型基元，最终构建出三维网格结构。对于化合物4，马来酸氢根阴离子呈现出典型的分子内低势垒氢键（LBHB）（S(7)型基元）。平面TPGH⁺阳离子与环状平面阴离子之间的氢键作用，形成了由16元环和42元环构成的褶皱状二维网格的层状固态结构。