i2c interrupt handling - single byte Tx

I am using MSP430F538 with bq40z50 as a slave device. As per the data sheet SLAU208N–June 2008–Revised May 2014 the single byte transmission to be handled as

"When transmitting a single byte of data, the UCTXSTP bit must be set while the byte is being transmitted or
anytime after transmission begins, without writing new data into UCBxTXBUF. Otherwise, only the
address is transmitted"

but as per my previous discussion from

https://e2e.ti.com/support/microcontrollers/msp430/f/166/t/347546

they said single byte transmission is possible by using interrupt. Since i have developed the interrupt code for transmission as follows

 // Vector 12: TXIFG  
        case 12:        
            if (nbytestoBeTxfr > 0)
            {
                    // Transfer next byte
                UCB0TXBUF = *data;
                nbytestoBeTxfr--;
                data++;
            } else
            {
                    // UCTXSTP - Generate Stop condition
                UCB0CTL1 |= UCTXSTP;
                    // Transfer completed
                    // Disable Transmit Interrupt
                UCB0IE &= ~UCTXIE;     
            } break;

If i see the output logic analyzer my slave device address only always send, and the SCL is keep on continuing even after stop bit generation, i never seen the data which to be send. Can anyone knows is the above way of handling is correct? I have seen some of the sample codes for i2c interrupt implementation, in that also they are developing the same way, but i am ending up with this issue. Could any one help me to solve this issue.

Also initial time the NACKIFG flag is set even the device is connected. After that it is not occurring and during that time i am facing the above said issue.

Thanks in advance