The interaction of Cu(II) with deuterated adsorbates in Cu(II)-ion-exchanged siliceous MCM-41 silica tube material was studied by electron spin resonance (ESR) and electron spin echo modulation (ESEM) techniques. It was found that polar adsorbates such as CH3OH and C5H5N remove Cu(II) from its ion exchange site to form [CU(CH3OH)(6)](2+) and [CU(C5H5N)(4)](2+) complexes. Cu(II) also forms complexes with two ethylenes and one benzene based on ESEM data. The ESR experiments suggest that dispersion forces of the adsorbed nonpolar molecules affect the location of the Cu(II) ions, but the cupric ions remain coordinated to framework oxygens in complexes formed with ethylene and benzene. The changes of the Cu(II) location induced by interaction with various adsorbates support weak bonding of the Cu(II) ions to the framework in siliceous MCM-41.