The state-owned Abu Dhabi Investment Authority will buy $7.5 billion in Citigroup Inc. securities, helping the nation’s largest bank by assets regain capital after record mortgage losses took out nearly half its market value, Bloomberg reported. After the transaction, Abu Dhabi, the largest emirate in the United Arab Emirates and owner of the world’s fifth-biggest oil reserves, will have a 4.9 percent stake in Citigroup, making it its largest shareholder.

The investment in securities that can be converted for as many as 235.6 million shares of stock starting in 2010 and yield 11 percent a year, almost double the interest Citigroup offers bond investors, will help satisfy the company’s need for cash. Its fourth-quarter profit is expected to be reduced by as much as $7 billion from losses related to subprime mortgages. These losses have led to CEO Charles O. Prince III’s departure and a 46 percent fall in its stock price.

Citigroup said Abu Dhabi would not have any role in the management or governance of the company.

Citigroup expects to restore its capital to targeted levels by the end of the second quarter next year, without cutting its quarterly dividend totaling $2.7 billion, according to a conference call with Robert Rubin, Citigroup chairman who took Prince’s place after he resigned, and Gary Crittenden, chief financial officer, that took place earlier this month.