Menaquinones and their semiquinone radical anions

Selected bond distances (A) for naphthoquinone (NQ), 2,3-dimethyl-naphthoquinone (23NQ), determined from X-ray diffraction(S7, SS) and B3LYP/6-31G(d) calculations.(60) Calculated 

Selected harmonic vibrational frequencies for MQ and MQ are displayed in Table 9.(60, 61) For the neutral MQ, the calculated antisymmetric and symmetric CO stretching modes appear at 1670 cm and 1665 cm, respectively, but are really too close together to distinguish reliably. Not far below the CO stretching modes is a C(2)=C(3) stretch at 1610 cm and two fused-ring C=C stretches at 1584 cm and 1570 cm. The scaled, calculated frequencies compare extremely well with the experimentally determined CO stretching modes measured at 1657 cm and 1672 cm, the C(2)=C(3) band observed at 1621 cm, and the C=C fiised-ring stretches at 1596 cm and 1582 cm. (59-97) All other experimentally measured vibrational bands listed in Table 9 are also extremely well reproduced by the calculations. In the radical anion MQ-, the CO stretches are shifted downward to 1501 cm for the antisymmetric stretch 

Approximate mode descriptions, experimentally measured vibrational frequencies(cm ),(59-91) and scaled calculated harmonic vibrational frequencies(cm )(50, 61) for selected normal modes of menaquinone(MQ) and its radical anion (MQ ). Calculations were done with the B3LYP/6-3 lG9d) method. Frequencies greater than 1000 cm were scaled by 0.9614 and 

Calculated(60) and experimental(P2) isotropic hyperfme coupling constants and spin densities for the menasemiquinone radical anion(MQ )- Calculations were done by using the 

Atom Expt. hfcc s Calc. Spin density Calc. 

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