González-Alvarez Almudena, Frontera Antoni, Ballester Pablo
Catalan Institution for Research and Advanced Studies (ICREA), Pg. Lluis Companys 23, 08010-Barcelona, Spain.
J Phys Chem B. 2009 Aug 20;113(33):11479-89. doi: 10.1021/jp9053742.
The molecular self-assembly of macrocycle 4 is induced by the simultaneous coordination of two molecules of 4-pyridyldiphenylphosphine 3, a highly selective ditopic ligand, to Zn-bisporphyrin 1 and a square-planar Pd(II) complex 2.COD. We report a detailed thermodynamic characterization of the assembly process based on the quantification of each one of the two metal(Zn,Pd)-ligand(N,P) pairwise binding interactions implicated in the supramolecular macrocycle and its effective molarity value (EM). The experimental values of the pairwise metal-ligand interactions have been derived from UV-vis, NMR titrations, and isothermal titration calorimetry experiments of reference model systems. In turn, an EM = 1 x 10(-2) M has been determined by relating the experimental overall stability constant determined for the cyclic assembly with the equation to evaluate the statistical (noncooperative) self-assembly equilibrium constant. We used numerical methods (SPECFIT program) to predict the solution behavior (speciation) of two mixtures of the three molecules 1, 3, and 2.COD in a 1:2:1 relative stoichiometry at two different overall concentrations. The method uses the overall stability constant values and the stoichiometries of eleven species (complexes) implicated in the multicomponent equilibrium self-assembly of 4. Estimated stability constants of some of the species were statistically determined. The agreement observed between the theoretical simulations and the experimental data validates the suitability of the theoretical treatment of self-assembly macrocyclization in a three component strategy.
大环化合物4的分子自组装是由两分子4-吡啶基二苯基膦3（一种高度选择性的双齿配体）与锌双卟啉1和平面正方形钯（II）配合物2.COD同时配位诱导产生的。我们基于对超分子大环中涉及的两种金属（锌、钯）-配体（氮、磷）成对结合相互作用中的每一种进行定量以及其有效摩尔浓度值（EM），报告了组装过程的详细热力学特征。成对金属-配体相互作用的实验值来自于参考模型体系的紫外-可见光谱、核磁共振滴定和等温滴定量热实验。反过来，通过将为环状组装测定的实验总稳定性常数与评估统计（非协同）自组装平衡常数的方程相关联，确定了EM = 1×10⁻² M。我们使用数值方法（SPECFIT程序）预测了三种分子1、3和2.COD以1:2:1相对化学计量比的两种混合物在两种不同总浓度下的溶液行为（物种形成）。该方法使用了涉及4的多组分平衡自组装的11种物质（配合物）的总稳定性常数和化学计量比。一些物质的估计稳定性常数是通过统计确定的。理论模拟与实验数据之间的一致性验证了在三组分策略中对自组装大环化进行理论处理的适用性。
