Solvent-Driven Conformational Landscapes of a Tetradentate Schiff Base Ligand and Its Metal Complexes: A Genetic Algorithm-Guided VCD Investigation.

Chiral salen ligands are a versatile platform for asymmetric catalysis, where understanding their conformational preferences is key to optimizing the stereo-inductive performance of their metal complexes. Here, we examine the conformational landscapes of (R)/(S)-N,N'-bis(3,5-di-tert-butylsalicylidene)-1-methyldiamine ligand and its Cu(II) and Ni(II) complexes in CDCl3 solution using vibrational circular dichroism (VCD) and infrared (IR) spectroscopy, supported by extensive conformational searches and DFT calculations. Contrary to its benign reputation, CDCl3 profoundly alters the ligand conformational landscape while leaving its metal complexes largely unaffected. This drastic yet selective solvent effect, missed by IR but captured by VCD, is interpreted using a genetic algorithm (GA) approach. Microsolvation modeling with Grimme's quantum cluster growth program reveals how weak solute-solvent van der Waals (vdW) interactions reshape conformational landscapes in CDCl3. The challenges in predicting the outcome of the delicate balance between intra-solute and solute-solvent vdW interactions are discussed in the context of current solvation models.