Who is "I" in Isaiah 44:6 I want to know who is "I" in Isaiah 44:6 in a view point of Trinity;


  The LORD is Israel’s king and defender. He is the LORD of Armies. This is what the LORD says: I am the first and the last, and there is no God except me.


I am tempted to think "I" is the Godhead of Trinity. But I am not sure the Godhead of "One Essence" of Trinity is the right concept to be able to speak like this. It seems to me that this act of speaking is more appropriate to a Person of Trinity. But then he says "no god besides me" and so I am confused.

Thanks in advance!
The reference to "the first and the last" is a conscious echo of Isaiah 41:4:


  Isaiah 41:4: Who hath wrought and done it, calling the generations from the beginning? I the LORD, the first, and with the last; I am he.  


Isaiah 41:4 is, in turn, part of a narrative about the Creator -- the first person of the Trinity --  as we see in Isaiah 40:28:


  Isaiah 40:28: Hast thou not known? hast thou not heard, that the everlasting God, the LORD, the Creator of the ends of the earth, fainteth not, neither is weary? there is no searching of his understanding.


In verse 44:24 the narrative again reminds us that it is God, the creator of all things, who is talking:


  Isaiah 44:24: Thus saith the LORD, thy redeemer, and he that formed thee from the womb, I am the LORD that maketh all things; that stretcheth forth the heavens alone; that spreadeth abroad the earth by myself;


The importance of "no God beside me" is not a denial of the Trinity but of paganism.  Most biblical scholars regard Isaiah chapters 40-55 to have been written during the Babylonian Exile by an anonymous prophet now known as Second Isaiah to distinguish him from Isaiah, son of Amoz. It was during this period that the priesthood began to assertively declare that there is only one God.