Severity: Warning
Message: file_get_contents(https://...@gmail.com&api_key=61f08fa0b96a73de8c900d749fcb997acc09): Failed to open stream: HTTP request failed! HTTP/1.1 429 Too Many Requests
Filename: helpers/my_audit_helper.php
Line Number: 143
Backtrace:
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 143
Function: file_get_contents
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 209
Function: simplexml_load_file_from_url
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 3098
Function: getPubMedXML
File: /var/www/html/application/controllers/Detail.php
Line: 574
Function: pubMedSearch_Global
File: /var/www/html/application/controllers/Detail.php
Line: 488
Function: pubMedGetRelatedKeyword
File: /var/www/html/index.php
Line: 316
Function: require_once
Severity: Warning
Message: Attempt to read property "Count" on bool
Filename: helpers/my_audit_helper.php
Line Number: 3100
Backtrace:
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 3100
Function: _error_handler
File: /var/www/html/application/controllers/Detail.php
Line: 574
Function: pubMedSearch_Global
File: /var/www/html/application/controllers/Detail.php
Line: 488
Function: pubMedGetRelatedKeyword
File: /var/www/html/index.php
Line: 316
Function: require_once
Despite the advances in host-guest chemistry, macrocyclic hosts with deep cavities are far from abundant among the large number of wholly synthetic hosts described in the literature. Herein, we describe the design and synthesis of two new tubular hosts, namely, corral[4]arene and corral[5]arene. The former has been isolated and characterized as two conformational diastereoisomers, one is centrosymmetric and the other asymmetric. The latter, a fivefold symmetrical and flexible host, has also been investigated in detail. It is composed of five 4,4'-dimethoxybiphenyl units bridged by ethynylene linkers at their 2,2'-positions and adopts a pentagonal conformation with a tubular-shaped cavity in the presence of guests. This structure endows corral[5]arene not only with a conjugated backbone, capable of bright fluorescent emission (quantum yield, 56%), but also a deep π-electron-rich aromatic cavity with remarkable conformational flexibility. The adaptive cavity of corral[5]arene allows it to accommodate a wide range of neutral and positively charged electron-deficient guests with different molecular sizes and shapes. Binding constants between this host and these guests in three different nonpolar organic solvents lie in the range of 10 to 10 M. Moreover, corral[5]arene exhibits dynamic chirality on account of the axes of chirality associated with each of the five biphenyl units and displays first-order transformation as exhibited by circular dichroism in response to the addition of chiral guests. All these stereochemical features render corral[5]arene an attractive host for a variety of supramolecular and nanotechnological applications.
Download full-text PDF |
Source |
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http://dx.doi.org/10.1021/jacs.2c08144 | DOI Listing |
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