Jantel Lavender made 1 of 2 free throws with 6.2 seconds left to break a 66-all tie, then Ohio State (27-5) made two defensive stops to seal the victory.
First two-time Big Ten defensive player of the year Shavelle Little knocked the ball away from Purdue point guard FahKara Malone, resulting in a scrum in front of the Purdue bench that was ruled a jump ball with 1.1 left.
The possession arrow favored the Boilermakers, who inbounded the ball to Brittany Rayburn, whose off-balance shot was far off the mark, and the Buckeyes began their first postseason celebration in three seasons.
Lavender, who was named most outstanding player of the tournament, scored 25 points and grabbed 13 rebounds – both game highs.
The sophomore center and OSU forward Star Allen (13 points) both scored in double figures for the third time in as many games, but this time faced a formidable post duo in Lindsay Wisdom-Hylton and Lakisha Freeman.
That Purdue pair was held scoreless in the first half but combined for 25 in the second, including 15 by Wisdom-Hylton. One or the other seemed to come up with a basket whenever the Boilermakers needed one down the stretch.
Wisdom-Hylton's last basket tied the game at 66 with 1:09 to go, then both teams traded empty possessions.
After Ohio State missed a chance to go ahead when Maria Moeller's three-point attempt was off the mark, the Buckeyes forced a shot clock violation at the other end.
Buckeye head coach Jim Foster called timeout with 12.2 left and called a play for Lavender, the two-time Big Ten player of the year. She got the ball to the right of the lane and put it on the floor, drawing a foul from Wisdom-Hylton as she tried to put up a shot.
"We wanted to get the ball to her," Foster said. "At that point of the game you've got to respect everything so that perimeter has got to come out and guard because you don't want to give up an uncontested shot, and it obviously created the opportunity to get the ball to her."
After missing the first free throw, she made what turned out to be the game winner.
"The first free throw I was letting my tiredness take over, and the second free throw I was like, ‘I gotta take my time, take a deep breath,' and I focused more and knocked it down," she said."
"Jantel was poised, especially after she missed the first one," Foster said. "I think a lot of times players will tank the second one after missing the first."
As for the final defensive stands, Foster knew the speed of Malone would allow her to cover enough floor to get her team into position for a good shot, so he instructed Little to give her enough room to prevent her from going by her.
"And I think she did an absolutely terrific job," he said. "And then the ball was exposed and she poked."
"I was supposed to go in the game and give a little cushion because she is fast, but I mean the way that everything was happening, the ball was literally right in front of me," Little said. "She crossed over right in front of me, and it was there, and I didn't want to lunge. I just wanted to tip, and I got a little tip and I thought I was going to come up with it but I got a tie-up."
More than half of the 7,293 fans turned out to root for Purdue, but a vocal contingent from Ohio State watched their Buckeyes earn a triumph that was two years in the making.
The last time they faced the Boilermakers in this game, Purdue jumped out to a 21-0 lead before hanging on for a 64-52 victory in 2007.
That was the first of what would be four consecutive postseason losses for Ohio State over a two-season span. Two weeks later they flopped in the NCAA tournament then last season bowed out in their first appearance at both the league and NCAA tournaments.
They hope to have taken major steps toward erasing the perception they can't win on the biggest stages by blowing away Illinois and Iowa in their first two games of this Big Ten tournament then outlasting Purdue.
"It's a very big deal," said senior Ashlee Trebilcock, who had eight points and three rebounds while gutting out 19 minutes on a bad right knee. "I'm so excited. We're all very excited. To lose in the first round last year and then to have that catastrophe against Purdue two years ago, this is a good feeling, and it was a great game. It came down to the wire, so it was a great game to have."
Rayburn led Purdue (22-10) with 20 points off the bench. The freshman guard was named to the all-tournament team along with Wisdom-Hylton, Lavender, Allen and Jenna Smith of Illinois.
The Buckeyes, who entered the weekend ranked 12th in the nation, earned the Big Ten's automatic bid to the NCAA tournament and will open play March 21 at Nationwide Arena in downtown Columbus. Their opponent will be announced March 16.