Magneto-optical properties and charge-spin coupling in the molecular (2,3-dmpyH)2CuBr4 spin-ladder material

We investigated the magnetic and optical properties of (2,3-dmpyH)(2)CuBr4, an unusual antiferromagnetic quantum spin ladder with strong rail interactions that can be saturated in a 30 T field. This transition drives a field-induced color change, a dramatic example of charge-spin coupling in a molecular material. Spin-density calculations reveal that electronic structure is sensitive to the magnetic state because magnetic orbital character depends on the spin arrangement between adjacent CuBr42- chromophores. This finding suggests that molecular architecture and the magnetic arrangement between molecular units might be used to control magnetochromism.