Well they actually have nothing to do with each other. Investment banking is an investment company function where a company invests money in other small companies. The typical function involved is financial.

Information systems [in a corporate environment] are related to the data systems used to support the operations of the business — from financial to manufacturing to marketing information is all held within corporation information systems.

source – i have an MBA with a concentration in information systems and have dealt with many investment bankers back in my dot-com days.