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DFT Computational Design of a Ligand‐Driven Light‐Induced Mechanism for Spin‐State Switching
Author(s) -
Starikova Alyona A.,
Minyaev Ruslan M.,
Starikov Andrey G.,
Minkin Vladimir I.
Publication year - 2013
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201300264
Subject(s) - chemistry , ligand (biochemistry) , ring (chemistry) , spin states , crystallography , photochromism , coordination sphere , coordination geometry , stereochemistry , photochemistry , molecule , crystal structure , inorganic chemistry , biochemistry , hydrogen bond , receptor , organic chemistry
A new ligand‐driven light‐induced spin‐state switching mechanism has been designed based on B3LYP*/6‐311++G(d,p) DFT calculations of a series of Co II , Ni II , and Cu II complexes with photochromic 2 H ‐chromene (2 H ‐1‐benzopyran) ligands 4 – 8 functionalized with N donor groups. The photoinduced electrocyclic rearrangements of the bis‐chelate four‐coordinate Ni II complexes with the ring‐closed forms of the ligands, all with high‐spin ground electronic states, are predicted to lead to the formation of a mixture of approximately equal amounts of the diamagnetic square‐planar and paramagnetic pseudo ‐tetrahedral isomers of these complexes containing ring‐opened o ‐quinonoid forms of the ligands. Of the Co II complexes, only that with the 2 H ‐chromen‐8‐amine ligand 4 exhibits the properties required for manifestation of the photoinitiated spin‐state switching. No local minima corresponding to four‐coordinate copper complexes with ring‐closed isomers of the functionalized 2 H ‐chromenes were located on the respective potential energy surfaces. In their ring‐closed forms, 2 H ‐chromenes react with Cu II ions to give two‐coordinate Cu I complexes, whereas ring‐opened o ‐quinonoid isomers form four‐coordinate bis‐chelate Cu II complexes. In the Ni II complexes with isomeric forms of 2 H ‐pyrano[3,2‐ h ]quinoline ligand 8 , the counterions Cl – and even BF 4 – enter into the coordination sphere of the central atom to form stable six‐coordinate metal complexes with high‐spin ground states. The predicted capacity of the Ni II complexes for light‐induced spin‐state switching is retained with the bulkier BPh 4 – counterion. The low‐spin state of the ion‐pair formed by the complex with the ring‐opened form of ligand 8 is 10.5 kcal mol –1 more energetically favorable than the high‐spin form.