Agree Frutiger Black's _C_ and _p_ would be a good basis for modification to make the logo. Also the top stroke on _a_.
But the lower bowl on _a_, with its compound curve to meet the vertical, is closer to Folio Bold http://www.myfonts.com/fonts/linotype/folio/ which also has a closer shape for the foot on the vertical stroke of _a_.
Don

Here are links to eps versions of the Capital One logo http://www.brandsoftheworld.com/logo/capital-one-2 http://www.brandsoftheworld.com/logo/capitalone-bank
Needless to say these are registered trademarks and use for anything other than examination of the design, without the express permission of the copyright and/or trademark holder, would raise legal issues.
Don