Riggs National Corp., in a move that officials linked to expanding growth opportunities, yesterday announced a major reorganization in senior management at the holding company and its principal subsidiary, Riggs National Bank.

The changes, which were announced after a joint meeting of the boards of the bank and holding company, indicate not only a decision to broaden the structure of the corporation but also a shift in the management philosophy and policies of Riggs' chairman and principal stockholder, Joe L. Allbritton, who has closely maintained control of the bank's and the holding company's operations.

Allbritton, who is chairman and chief executive officer of both Riggs National Corp. and Riggs National Bank, will retain those positions. As part of the reorganization announced yesterday, however, George P. Clancy Jr. was named president and chief operating officer of Riggs National Corp., making him the first person to hold the title of chief operating officer since the holding company was formed in 1982. Meanwhile, Timothy C. Coughlin was appointed president and chief operating officer of Riggs National Bank.

Both Clancy and Coughlin had been executive vice presidents at the bank.

Frank L. Langhammer III, executive vice president in charge of the bank's corporate and commercial banking groups, was appointed to the new position of senior executive vice president and chairman of the bank's loan committee. As chairman of that committee, Langhammer will supervise all lending activities of the bank.

In another management change, Thomas W. Wren, vice chairman of the bank and a close associate of Allbritton for several years, was promoted to vice chairman of Riggs National Corp. Wren, who most recently had been president of the corporation, is a director of the bank and holding company.

Allbritton bought control of Riggs Bank in 1981 and, while chairman of the holding company, assumed the positions of chairman and chief executive officer of the bank in 1983 in a major shakeup that led to the resignation of former chairman and chief executive officer Vincent C. Burke Jr.

Allbritton, who spent $70 million in acquiring more than 40 percent of Riggs' stock, took full management control after the bank's earnings began to decline and problem loans began to surface. Riggs, which is Washington's biggest banking institution, reported record profits of $26.9 million last year, an increase of 15 percent. Assets totaled $5.1 billion at the end of 1984.

Although banking sources had speculated that Allbritton would soon delegate more responsibility in operating the bank, there was no indication that a major reorganization would occur this soon.

"Riggs Bank is today in excellent shape," Allbritton said in a prepared statement yesterday. "Our expectations of future growth, coupled with the possibilities of new opportunities through interstate banking, make this an especially propitious time to broaden Riggs' strong, cohesive team of top management at both the bank and corporation levels," he continued.

Coughlin, 42, who will direct day-to-day operations of the bank, joined Riggs in 1983 as an executive vice president in the office of the chief executive officer. He previously worked at major banks in New York.

Clancy, 41, headed Riggs' London office from 1982 to 1984. A native of the District, he has been with Riggs since beginning in his career in banking in 1967.

Langhammer joined Riggs as a senior vice president in 1982, after working for several years at a New York bank.