The jauntily slant-top Citicorp Center, the newest addition to Manhattan's famed skyscraper silhouette, was formally dedicated earlier this week and is already a notable success is terms of economics, architecture, planning and energy conservation.

Constructed in a period when few other buildings were going up in New York - because of a deeply depressed real estate market that was also saturated with office space - the 59-story Citicorp Center opens almost fully leased. Its rates are considered premium, even in the high-rent Midtown office district where it is located.

The building moreover, is fully on schedule (the first tenants moved in last April and last details will be finished in the early months of 1978), and even more remarkably, comes in a shade below the $150 million that was budgeted for it.

Designed by Hugh Stubbins & Associates of Cambridge, Mass., the building will not please those nos- talgic for skyscraper fantasies nor modernists looking for some novel breakthrough. But the 915-foot building is both distinctive and elegant, with many unusual architectural features.

It rises airily on four 127-foot columns from a sunken plaza, leaving a maximum amount of space on the ground level for passersby.

Tucked into one corner of the Citicorp Center's block at Lexington between 53rd and 54th streets is the free-standing structure of St. Peter's Lutheran Church, which originally occupied space on the block, and which has been rebuilt in a dramatically modern mode.

Also at the base of the center is a seven-story lowrise structure housing three floors of "The Market," a complex of about 20 international restaurants and food- and houseware-related stores. The Market, it is hoped, will be a New York equivalent of complex like San Francisco's Chiardelli Square, attracting both regular shoppers and tourists.

Although multi-use office buildings have proved popular in other cities, particularly Chicago, the Citicorp Center is one fo the first attempts in New York City at successfully integrating an office tower with a shopping complex. (At one time inclusion of about 100 apartments was also contemplated. But the idea was discarded because of the expense of maintining 24-hour-a-day ancillary services.)

The Market will be open seven days a week and the Plaza which leads into it has direct access to a station of the New York subway system.

The tower itself has the linearity of a computer punch card with bands of double-glazed reflective windows alternating with a light aluminum skin that is creamy rather than shiny in its lutre.

What really makes the building distinctive, however, is the 45-degree sloping top that lets it vie with the other "crowned heads" of New York City such as the Chrysler Building and the Empire State Building.

Its 915-feet make it the fourth tallest building in New York City, after the World Trade Center twin towers and the Chrysler and Empire State buildings, and the eighth tallest building in the world.

The 160-foot angled crown is not occupied by floor space but contains a "tuned mass damper," a 400-ton floating concrete block, controlled by computers, that is designed to move out of phase with the tower's motion during high winds and thus reduce sway by about 40 per cent.

The slope was originally supposed to contain a solar collector to gather the sun's rays for partial energy generation, but Citicorp, the holding company for the world's second largest bank, dropped the idea when it discovered that it could cost more than electricity. But conversations are continuing with Consolidated Edison Co. about some kind of solar energy system, according to officials.

The building already has several features designed to conserve energy, however, including a heat pump that reclaims heat generated by lights, occupants, and other heat-producing elements and recirculates it through induction units at the perimeter of the building. The double-glazed reflective glass that covers 46 per cent of the building's surface is also meant to reduce heat loss and gain.

Citicorp is occupying 650,000 square feet on 26 of the building's 59 floors and is leasing out the rest. The headquarters offices of Citicorp will continue to be at 399 Park Ave. across the street.

Leasing rates range from about $15 a square foot to as high as $25 a square foot.

"When people first heard of the prices we were going to charge for office space, some of the brokers around town laughed at us," said DeFord.

"But with what little prime space there is to let today, everyone has jacked up their prices," he added. "Now there isn't a good building with any sizeable block of space in Midtown Manhattan."