The RiverCity Co. is buying nearly half a city block in the heart of downtown to set the stage for the revival of a string of mostly empty buildings.

“As a community, we’ve spent a lot of time focusing on Ross’s Landing and the North Shore. We’re long overdue committing time, money and resources to the central business district,” said Ken Hays, who heads the downtown development group.

RiverCity, which plans to formally announce the purchase this afternoon, is buying six structures on the east side of the 700 block of Market Street. Except for the high-rise SunTrust Bank building and a few small businesses, the block is vacant, The private, nonprofit group is buying the buildings from 710 to 722 Market St., said Mr. Hays. The structures sit in the center of the block between the Downtown Mart and SunTrust Bank. They have about 175 feet of street frontage, Mr. Hays said.

The aim is to look at combining their floor space and making it cheaper and easier for developers to step in and reuse the property. A roadblock to the redevelopment of the buildings is the expense of rehabilitating each individual structure to meet today’s codes.

“That’s one of the big reasons they have not been developed over the past 25 years,” Mr. Hays said. RiverCity foresees developers putting retail on ground level and housing on the floors above. The buildings range from two to four stories high.

While the riverfront and Southside are active, downtown’s central business district has lagged. Business after business has closed in the area, leaving dark or shuttered storefronts. Earlier this year, longtime downtown staple Waldenbooks shut down. Fountain Drug, the area’s only drug store, closed soon afterward.

This summer, RiverCity pledged it would focus on stimulating more business and use of buildings in the 600, 700 and 800 blocks of Market. Officials spoke of possibly creating through-block parks, similar to the busy Jack’s Alley development on the 400 block.

Ann Coulter, RiverCity’s executive vice president, said the group’s purchase of much of the 700 block is to create street activity.

“We want to make it a 24-hour kind of place,” she said.

Mr. Hays said plans are to hire a design team to examine the layout of the buildings. Also, RiverCity will look for one or more developers.

“The ideal situation is we hope to find a developer that may have experience in doing something similar,” he said.

Mayor Jon Kinsey, a developer himself before taking office, agreed that combining the buildings is critical to their redevelopment.

“Separately, store widths are smaller than ideal. Having them combined, they can share elevator costs and common area costs critical in having upper levels redeveloped,” he said.

RiverCity hopes its action on the 700 block will send a signal to other building owners and developers about upgrading their central city properties. RiverCity said the purchases equal nearly 48,000 square feet of space.

Ms. Coulter said most of the buildings are nearly 100 years old. She said in the 1930s to 1960s, the area bustled with activity and a variety of businesses.

“These buildings offer a unique opportunity to recreate that,” she said.

Two of the buildings being acquired by RiverCity have tenants. Apollo’s Market Street Grille opened a couple of months ago.

“The Apollo figures in very well in the mix,” said Mr. Hays.

Mr. Hays declined to give the purchase price of the buildings. While contracts have been signed, the deals haven’t closed yet, he said.

The mayor said the activity on the 700 block fits with planned redevelopment on the opposite ends of the central business district on Market.