London Stock Exchange (LSE) has agreed to buy Citigroup's fixed-income analytics platform and index business for $685 million in cash, the companies said on Tuesday.

LSE, which has said it would explore investments to drive growth after the collapse of its proposed merger with Deutsche Boerse, said the deal would boost the data and analytics capabilities of its information services and FTSE Russell franchise businesses, including an increase in benchmark assets under management to about $15 trillion.

The deal, which is subject to regulatory clearance and is expected to close in the second half of this year, will add $30 million to LSE's revenue over the first three years after completion and bring $18 million of cost savings.

LSE expects its core profit margin to rise to at least 50 percent within three years of the deal's completion, the company said.