Investor Jeffrey Cohen's bid to take over the Bank of Columbia on behalf of a group of young businessmen and women appeared sure of success yesterday with approximately 96 percent of the bank's stock offered for sale to the group.

The Cohen group's offer to purchase the bank's stock at $16 a share expired at 5 p.m. yesterday. The stock had been trading at between $10 and $15 in recent months since news of the proposed tender offer became public. No final figure was available on the exact number of shares tendered, but it appeared to be at least 425,000 of the 439,565 shares of common stock.

Cohen said the group plans no management changes for the $48.4 million asset bank, the 13th-largest in the city. But he added, "The bank is going to wake up. It will be a more responsive and aggressive bank."

Cohen's approximately 40 coinvestors include a range of relatively young business officials and entrepreneurs. The group includes, among others, Peggy Cooper, who heads the city's commission on the arts, advertising executive Stuart Karu, attorney Samuel C. Jackson, architect Theodore Mariani, Thomas Warner of the George F. Warner & Co. plumbing company and Stuart Long, owner of the Capitol Hill restaurant The Hawk & Dove.

"They're generally men and women who have developed and own their own businesses," said Cohen.

Cohen offered to buy all the stock of the Bank of Columbia for $7 million at the same time he was negotiating to acquire a majority interest in the Hemisphere National Bank, a transaction that subsequently ran into difficulties.