Gavara Raquel, Aguiló Elisabet, Fonseca Guerra Célia, Rodríguez Laura, Lima João Carlos
†Departament de Química Inorgànica, Universitat de Barcelona, Barcelona, Barcelona 08028, Spain.
‡Department of Theoretical Chemistry and Amsterdam Center for Multiscale Modeling, VU University, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands.
Inorg Chem. 2015 Jun 1;54(11):5195-203. doi: 10.1021/acs.inorgchem.5b00025. Epub 2015 May 20.
The complexes [Au(4-pyridylethynyl)(phosph)] (phosph = PTA (1), DAPTA (2)) are known to produce supramolecular aggregates and gels in water. We studied the impact of these aggregation processes in the absorption spectra, (1)H NMR (at different temperatures and concentrations), and DLS and estimated the equilibrium constant for a single step aggregation of the molecule (K = 26760 and 2590 M(-1) for 1 and 2, respectively, at 25 °C). We present spectroscopic evidence for the presence of Au···Au contacts in the aggregates: the recorded changes on (1)H NMR and the appearance of new absorption bands assigned to (σAu···Au-π) have been attributed to the short (Au···Au) average distances in the aggregates. Relativistic density functional theory computations support the existence of short Au···Au distances and reveal charge-transfer in the aurophilic interactions. The free energy for a single step aggregation was calculated from the experimental data, and the value obtained (ΔG ∼ -20 kJ/mol) is in good agreement with the expected values in the order of the energies found for hydrogen bonds. The DFT computations confirm the experimental findings that aggregation of monomer 1 is stronger than the aggregation of monomer 2 and the existence of aurophilic interactions.
已知配合物[Au(4 - 吡啶乙炔基)(膦)]（膦 = PTA (1)，DAPTA (2)）在水中会形成超分子聚集体和凝胶。我们研究了这些聚集过程对吸收光谱、¹H NMR（在不同温度和浓度下）以及动态光散射的影响，并估算了该分子单步聚集的平衡常数（在25°C时，1和2的K分别为26760和2590 M⁻¹）。我们提供了聚集体中存在金···金接触的光谱证据：¹H NMR记录的变化以及归属于(σAu···Au - π)的新吸收带的出现，归因于聚集体中较短的（金···金）平均距离。相对论密度泛函理论计算支持了短金···金距离的存在，并揭示了亲金相互作用中的电荷转移。根据实验数据计算了单步聚集的自由能，得到的值（ΔG ∼ -20 kJ/mol）与氢键能量顺序中的预期值吻合良好。密度泛函理论计算证实了实验结果，即单体1的聚集比单体2的聚集更强，且存在亲金相互作用。
