Actually, they are all 4th century.
During the years of conflict between East and West, the Roman pontiff remained firm, defending the Catholic faith against heresies and unruly or immoral secular powers, especially the Byzantine emperor. The first conflict came when Emperor Constantius appointed an Arian heretic as patriarch. Pope Julian excommunicated the patriarch in 343, and Constantinople remained in schism until John Chrysostom assumed the patriarchate in 398.
catholic.com/library/Eastern_Orthodoxy.asp
St. Gregory was Archbishop of Constantinople 379-381, i.e. between 343 and 398.
Not only did Basil’s representative have to travel from Cæsarea to Armenia, and from Armenia to Alexandria, he also had to go to Rome to obtain the sanction of Pope Damasus and the acquiescence of the West. Notwithstanding the blunder committed at Antioch in 363, the generous spirit of Athanasius gave hope of success, his sudden death, however (May, 373), caused all efforts to be abandoned. Even at Rome and in the West, Basil and Meletius were to meet with disappointement. While they wrought persistently to restore peace, a new Antiochene community, declaring itself connected with Rome and Athanasius, increased the number of dissidents, aggravated the rivalry, and renewed the disputes. There were now three Antiochene churches that formally adopted the Nicene Creed. The generous scheme of Basil for appeasement and union had ended unfortunately, and to make matters worse, Evagrius, the chief promoter of the attempted reconciliation, once more joined the party of Paulinus. This important conversion won over to the intruders St. Jerome and Pope Damasus; the very next year, and without any declaration concerning the schism, the pope showed a decided preference for Paulinus, recognized him as bishop, greeted him as brother, and considered him papal legate in the East…Two legates sent to Rome, Dorotheus and Sanctissimus, returned in the spring of 377, bringing with them cordial declarations which St. Basil instantly proceeded to publish everywhere. These declarations pronounced anathemas against Arius and the heresy of Apollinaris then spreading at Antioch, condemnations all the more timely, as theological excitement was then at its highest in Antioch, and was gradually reaching Palestine. St. Jerome entered into the conflict, perhaps without having a thorough knowledge of the situation. Rejecting Meletius, Vitalian, and Paulinus, he made a direct appeal to Pope Damasus in a letter still famous, but which the pope did not answer. Discontented, Jerome returned to Antioch, let himself be ordained presbyter by Paulinus, and became the echo of Paulinist imputations against Meletius and his following…Since the two factions which divided the Antiochene Church were orthodox there remained but to unite them actually, a difficult move, but easy when the death of either bishop made it possible for the survivor to exercise full authority without hurting pride or discipline. This solution Meletius recognized as early as 381, but his friendly and peace- making proposals were rejected by Paulinus who refused to come to any agreement or settlement.
newadvent.org/cathen/10161b.htm
Paulinus was Rome’s man in Antioch, not Meletius, who died in 381.
In the East Siricius interposed to settle the Meletian schism at Antioch; this schism had continued notwithstanding the death in 381 of Meletius at the Council of Constantinople. The followers of Meletius elected Flavian as his successor, while the adherents of Bishop Paulinus, after the death of this bishop (388), elected Evagrius. Evagrius died in 392 and through Flavian’s management no successor was elected. By the mediation of St. John Chrysostom and Theophilus of Alexandria an embassy, led by Bishop Acacius of Beroea, was sent to Rome to persuade Siricius to recognize Flavian and to readmit him to communion with the Church.
newadvent.org/cathen/14026a.htm
At the time of Siricius’ death (399), Rome still did not recognize Flavian.
