Can i send one photo from lightroom LrC on a mac via text imessage

There is no direct way, but it’s still easy. There is no need to create a collection.

Select the photo and choose File > Export. Set up the file format and size the way you want it, and export to the desktop or any folder on your Mac. Then, if you have set up the Messages app on your Mac to send and receive texts through an iPhone, open the Messages app, and drag the exported image from the desktop and drop it into the message.

So that’s it, just export the image and then drag it into the text message.

Or, if the image in the catalog is unedited and it’s already an acceptable format and size for a text message (such as JPEG), you could drag it directly from the Lightroom Classic grid or filmstrip, and drop it into Messages. But images edited in Lightroom Classic must be exported to incorporate those edits.