As mentioned above, the a1 band is either missing or hidden in the noise in the spectra of [(bipy)CuCl] + system, Figure . Calculations of Cs-symmetric [(bipy)CuCl] + with Cl artificially bent by 20 degrees from the C2v minimum give calc (a1) = 679 nm with oscillator strength ~ 0.003 that is only ca 10x higher than in the C2v minimum. Apparently, the vibronic coupling is much weaker in [(bipy)CuCl] + and the corresponding band is not well observed in the spectrum.