The shift of X-ray powder pattern of Platinum(II) complexes was observ
ed under light irradiation by using X-ray powder diffractometer. The p
eaks were returned to the original one when the irradiation of light w
as cut off. The observed X-ray powder patterns show that the unit cell
of [Pt(acac)(2)] is expanded under light irradiation, however, that o
f [Bu4N](4)[Pt-2(pop)(4)] (pop(2-)=P2O5H22-) is contracted.